Add a missing return statement after a result.error response is sent.

android/src/main/java/com/baseflow/permissionhandler/PermissionHandlerPlugin.java

@@ -202,6 +202,7 @@ public class PermissionHandlerPlugin implements MethodCallHandler {
               "ERROR_ALREADY_REQUESTING_PERMISSIONS",
               "ERROR_ALREADY_REQUESTING_PERMISSIONS",
               "A request for permissions is already running, please wait for it to finish before doing another request (note that you can request multiple permissions at the same time).",
               "A request for permissions is already running, please wait for it to finish before doing another request (note that you can request multiple permissions at the same time).",
               null);
               null);
+          return;
         }
         }
 
 
         mResult = result;
         mResult = result;