Fixing BadTokenException while showing FIAM (#2402)

Fixing BadTokenException while showing FIAM.

Related Bug : #2107

This is a possible fix as the BadTokenException usually happens when we try to add/show new views with a finishing activity context.

Author: eldhosembabu

firebase-inappmessaging-display/src/main/java/com/google/firebase/inappmessaging/display/internal/FiamWindowManager.java

@@ -54,6 +54,11 @@ public void show(@NonNull final BindingWrapper bindingWrapper, @NonNull Activity
       return;
     }
 
+    if (activity.isFinishing()) {
+      Logging.loge("Activity is finishing or does not have valid window token. Cannot show FIAM.");
+      return;
+    }
+
     InAppMessageLayoutConfig config = bindingWrapper.getConfig();
     final WindowManager.LayoutParams layoutParams = getLayoutParams(config, activity);