fix(share_plus): Avoid crash on iOS during file and text sharing in add-to-app scenario (#3738)

Author: outring

packages/share_plus/share_plus/ios/share_plus/Sources/share_plus/FPPSharePlusPlugin.m

@@ -377,14 +377,14 @@ + (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar> *)registrar {
                       withSubject:shareTitle
                          withText:shareText
             excludedActivityTypes:excludedActivityTypes
-                   withController:rootViewController
+                   withController:topViewController
                          atSource:originRect
                          toResult:result];
       } else if (shareText) {
         [self shareText:shareText
                           subject:shareTitle
             excludedActivityTypes:excludedActivityTypes
-                   withController:rootViewController
+                   withController:topViewController
                          atSource:originRect
                          toResult:result];
       } else {