fix(ios): properly detect when optional callback is not supplied

The new JSC API will give us a JSValue* that represents undefined.
We only checked the pointer/value was nil. We need to guard for nil
and verify the JSValue is a function (or not use/call the callback)

Fixes TIMOB-27846

iphone/Classes/PlatformModule.m

@@ -309,6 +309,12 @@ - (BOOL)openURL:(NSString *)url withOptions:(JSValue *)options andCallback:(JSVa
   } else if ([options isObject]) {
     optionsDict = [options toDictionary];
   }
+  // Ensure callback is actually a function. If not, make it nil so we don't fire it
+  // Since callback is optional, this may be a JSValue representing 'undefined' here wich is not nil
+  // So we need this special guard
+  if (![callback isFunction]) {
+    callback = nil;
+  }
 
   if (newUrl != nil) {
     [[UIApplication sharedApplication] openURL:newUrl

iphone/Classes/TiNetworkBonjourServiceProxy.m

@@ -227,7 +227,7 @@ - (void)publish:(JSValue *)socketProxy withCallback:(JSValue *)callback
                                             port:[port intValue]];
   [service setDelegate:self];
 
-  if (callback != nil) {
+  if (callback != nil && [callback isFunction]) {
     publishCallback = [callback retain];
   }
   [service publish];
@@ -261,7 +261,7 @@ - (void)resolve:(NSTimeInterval)timeout withCallback:(JSValue *)callback
     timeout = 120.0;
   }
 
-  if (callback != nil) {
+  if (callback != nil && [callback isFunction]) {
     resolveCallback = [callback retain];
   }
 
@@ -270,7 +270,7 @@ - (void)resolve:(NSTimeInterval)timeout withCallback:(JSValue *)callback
 
 - (void)stop:(JSValue *)callback
 {
-  if (callback != nil) {
+  if (callback != nil && [callback isFunction]) {
     stopCallback = [callback retain];
   }
   [service stop];