fix handle multiple identical instances in memory

This is done by avoid removing instance
from cached _instances map on dispose.

The bug happened when there were two identical pages
in memory and one of them was disposed,
thus removing the cached instance also for the
other page instance and leaving
a circular progress indicator spinning forever.

lib/src/screens/commit_detail/controller_commit_detail.dart

@@ -8,7 +8,7 @@ class _CommitDetailController with ShareMixin {
     }
 
     if (instance != null && args.commitId != instance!.args.commitId) {
-      instance = _CommitDetailController._(args, apiService);
+      instance = null;
     }
 
     instance ??= _CommitDetailController._(args, apiService);
@@ -46,7 +46,6 @@ class _CommitDetailController with ShareMixin {
 
   void dispose() {
     instance = null;
-    _instances.remove(args.hashCode);
   }
 
   Future<void> init() async {

lib/src/screens/commits/controller_commits.dart

@@ -12,7 +12,7 @@ class _CommitsController with FilterMixin {
     }
 
     if (instance != null && args != instance!.args) {
-      instance = _CommitsController._(apiService, storageService, args);
+      instance = null;
     }
 
     instance ??= _CommitsController._(apiService, storageService, args);
@@ -40,7 +40,6 @@ class _CommitsController with FilterMixin {
 
   void dispose() {
     instance = null;
-    _instances.remove(args);
   }
 
   Future<void> init() async {

lib/src/screens/member_detail/controller_member_detail.dart

@@ -8,7 +8,7 @@ class _MemberDetailController {
     }
 
     if (instance != null && instance!.userDescriptor != userDescriptor) {
-      instance = _MemberDetailController._(userDescriptor, apiService);
+      instance = null;
     }
 
     instance ??= _MemberDetailController._(userDescriptor, apiService);
@@ -31,7 +31,6 @@ class _MemberDetailController {
 
   void dispose() {
     instance = null;
-    _instances.remove(userDescriptor);
   }
 
   Future<void> init() async {

lib/src/screens/pipeline_detail/controller_pipeline_detail.dart

@@ -8,7 +8,7 @@ class _PipelineDetailController with ShareMixin {
     }
 
     if (instance != null && args.id != instance!.args.id) {
-      instance = _PipelineDetailController._(args, apiService);
+      instance = null;
     }
 
     instance ??= _PipelineDetailController._(args, apiService);
@@ -39,7 +39,6 @@ class _PipelineDetailController with ShareMixin {
     _stopTimer();
 
     instance = null;
-    _instances.remove(args.hashCode);
   }
 
   void _stopTimer() {

lib/src/screens/pipelines/controller_pipelines.dart

@@ -12,7 +12,7 @@ class _PipelinesController with FilterMixin {
     }
 
     if (instance != null && args != instance!.args) {
-      instance = _PipelinesController._(apiService, storageService, args);
+      instance = null;
     }
 
     instance ??= _PipelinesController._(apiService, storageService, args);
@@ -53,7 +53,6 @@ class _PipelinesController with FilterMixin {
     _stopTimer();
 
     instance = null;
-    _instances.remove(args.hashCode);
   }
 
   void _stopTimer() {

lib/src/screens/project_detail/controller_project_detail.dart

@@ -8,8 +8,9 @@ class _ProjectDetailController {
     }
 
     if (instance != null && instance!.projectName != projectName) {
-      instance = _ProjectDetailController._(apiService, projectName);
+      instance = null;
     }
+
     instance ??= _ProjectDetailController._(apiService, projectName);
     return _instances.putIfAbsent(projectName, () => instance!);
   }
@@ -37,7 +38,6 @@ class _ProjectDetailController {
 
   void dispose() {
     instance = null;
-    _instances.remove(projectName);
   }
 
   Future<void> init() async {

lib/src/screens/pull_request_detail/controller_pull_request_detail.dart

@@ -11,7 +11,7 @@ class _PullRequestDetailController with ShareMixin, AppLogger, PullRequestHelper
     }
 
     if (instance != null && instance!.args != args) {
-      instance = _PullRequestDetailController._(args, apiService);
+      instance = null;
     }
 
     instance ??= _PullRequestDetailController._(args, apiService);
@@ -65,7 +65,6 @@ class _PullRequestDetailController with ShareMixin, AppLogger, PullRequestHelper
 
   void dispose() {
     instance = null;
-    _instances.remove(args.hashCode);
   }
 
   Future<void> init() async {

lib/src/screens/pull_requests/controller_pull_requests.dart

@@ -12,7 +12,7 @@ class _PullRequestsController with FilterMixin {
     }
 
     if (instance != null && project?.id != instance!.project?.id) {
-      instance = _PullRequestsController._(apiService, storageService, project);
+      instance = null;
     }
 
     instance ??= _PullRequestsController._(apiService, storageService, project);
@@ -47,7 +47,6 @@ class _PullRequestsController with FilterMixin {
 
   void dispose() {
     instance = null;
-    _instances.remove(project.hashCode);
   }
 
   Future<void> init() async {

lib/src/screens/repository_detail/controller_repository_detail.dart

@@ -8,7 +8,7 @@ class _RepositoryDetailController {
     }
 
     if (instance != null && instance!.args != args) {
-      instance = _RepositoryDetailController._(apiService, args);
+      instance = null;
     }
 
     instance ??= _RepositoryDetailController._(apiService, args);
@@ -33,7 +33,6 @@ class _RepositoryDetailController {
 
   void dispose() {
     instance = null;
-    _instances.remove(args.hashCode);
   }
 
   Future<void> init() async {

lib/src/screens/work_item_detail/controller_work_item_detail.dart

@@ -12,7 +12,7 @@ class _WorkItemDetailController with ShareMixin, FilterMixin, AppLogger {
     }
 
     if (instance != null && instance!.args != args) {
-      instance = _WorkItemDetailController._(args, apiService, storageService);
+      instance = null;
     }
 
     instance ??= _WorkItemDetailController._(args, apiService, storageService);
@@ -49,7 +49,6 @@ class _WorkItemDetailController with ShareMixin, FilterMixin, AppLogger {
 
   void dispose() {
     instance = null;
-    _instances.remove(args.hashCode);
   }
 
   Future<void> init() async {

lib/src/screens/work_items/controller_work_items.dart

@@ -12,7 +12,7 @@ class _WorkItemsController with FilterMixin {
     }
 
     if (instance != null && project?.id != instance!.project?.id) {
-      instance = _WorkItemsController._(apiService, storageService, project);
+      instance = null;
     }
 
     instance ??= _WorkItemsController._(apiService, storageService, project);
@@ -58,7 +58,6 @@ class _WorkItemsController with FilterMixin {
 
   void dispose() {
     instance = null;
-    _instances.remove(project.hashCode);
   }
 
   Future<void> init() async {