adding a null check at closing search

app/src/main/kotlin/com/simplemobiletools/gallery/activities/MediaActivity.kt

@@ -137,8 +137,10 @@ class MediaActivity : SimpleActivity(), MediaAdapter.MediaOperationsListener {
 
     override fun onStop() {
         super.onStop()
+        if (mSearchMenuItem != null) {
             MenuItemCompat.collapseActionView(mSearchMenuItem)
         }
+    }
 
     override fun onDestroy() {
         super.onDestroy()