Add null check on show()

Adding a null check on show() in DevLoadingModule which seems to have been missed.

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/modules/devloading/DevLoadingModule.java

@@ -40,7 +40,9 @@ public void showMessage(final String message, final Double color, final Double b
         new Runnable() {
           @Override
           public void run() {
-            mDevLoadingViewManager.showMessage(message);
+            if (mDevLoadingViewManager != null) {
+              mDevLoadingViewManager.showMessage(message);
+            }
           }
         });
   }