Fix Snackbar not dismissing bug

When Snackbar was displayed while another Snackbar was displayed,
the last ref to the current Snackbar was removed and it didn't get removed
when onScreenChange was called.

android/app/src/main/java/com/reactnativenavigation/views/SnackbarAndFabContainer.java

     }
 
     @Override
-    public void onDismiss() {
-        snakbar = null;
+    public void onDismiss(Snakbar snakbar) {
+        if (this.snakbar == snakbar) {
+            this.snakbar = null;
+        }
     }
 
     public void destroy() {

android/app/src/main/java/com/reactnativenavigation/views/Snakbar.java

     private Snackbar snackbar;
 
     public interface OnDismissListener {
-        void onDismiss();
+        void onDismiss(Snakbar snakbar);
     }
 
     public void show() {
 
             @Override
             public void onViewDetachedFromWindow(View v) {
-                parent.onDismiss();
+                parent.onDismiss(Snakbar.this);
             }
         });
     }