do not show "switch" menu item on file details/preview text/video/audio

src/com/owncloud/android/ui/preview/PreviewTextFragment.java

@@ -290,6 +290,12 @@ public class PreviewTextFragment extends FileFragment {
             item.setVisible(false);
             item.setEnabled(false);
         }
+
+        item = menu.findItem(R.id.action_switch_view);
+        if (item != null){
+            item.setVisible(false);
+            item.setEnabled(false);
+        }
     }
 
     /**