Fix bug in globalcontext_unregister_process

The way the registered processes were freed when being unregisterd was unsafe if
future API changes requre adjusting the layout of the RegisteredProcess struct.

Signed-off-by: Winford <winford@object.stream>

src/libAtomVM/globalcontext.c

@@ -302,10 +302,10 @@ bool globalcontext_unregister_process(GlobalContext *glb, int atom_index)
     struct ListHead *registered_processes_list = synclist_wrlock(&glb->registered_processes);
     struct ListHead *item;
     LIST_FOR_EACH (item, registered_processes_list) {
-        const struct RegisteredProcess *registered_process = GET_LIST_ENTRY(item, struct RegisteredProcess, registered_processes_list_head);
+        struct RegisteredProcess *registered_process = GET_LIST_ENTRY(item, struct RegisteredProcess, registered_processes_list_head);
         if (registered_process->atom_index == atom_index) {
             list_remove(item);
-            free(item);
+            free(registered_process);
             synclist_unlock(&glb->registered_processes);
             return true;
         }