fix: Share UI will be closed if the selected app was "cancelled" (#973)

Side effect: Share UI will be closed if the selected app was "cancelled", instead of causing a crash due to duplicate callback calls.

Co-authored-by: Cristiano Coelho <cristianocca@hotmail.com>

ios/RNShare.m

@@ -262,13 +262,23 @@ - (NSDictionary *)constantsToExport
         shareController.excludedActivityTypes = excludedActivityTypes;
     }
 
+    __weak UIActivityViewController* weakShareController = shareController;
     shareController.completionWithItemsHandler = ^(NSString *activityType, BOOL completed, __unused NSArray *returnedItems, NSError *activityError) {
+
+        // always dismiss since this may be called from cancelled shares
+        // but the share menu would remain open, and our callback would fire again on close
+        [controller dismissViewControllerAnimated:true completion:nil];
+
         if (activityError) {
-            [controller  dismissViewControllerAnimated:true completion:nil];
             failureCallback(activityError);
         } else {
             successCallback(@[@(completed), RCTNullIfNil(activityType)]);
         }
+
+        // clear the completion handler to prevent cycles
+        if(weakShareController){
+            weakShareController.completionWithItemsHandler = nil;
+        }
     };
 
     shareController.modalPresentationStyle = UIModalPresentationPopover;