Fix code analysis

Signed-off-by: Jonas Mayer <jonas.a.mayer@gmx.net>

app/src/main/java/com/owncloud/android/ui/preview/PreviewTextStringFragment.java

@@ -111,11 +111,9 @@ public class PreviewTextStringFragment extends PreviewTextFragment {
 
     @Override
     public void onStart() {
-        if (isEditorWebviewLaunched) {
-            if (containerActivity instanceof FileDisplayActivity fileDisplayActivity) {
-                fileDisplayActivity.getSupportFragmentManager().popBackStack();
-                fileDisplayActivity.onRefresh();
-            }
+        if (isEditorWebviewLaunched && containerActivity instanceof FileDisplayActivity fileDisplayActivity) {
+            fileDisplayActivity.getSupportFragmentManager().popBackStack();
+            fileDisplayActivity.onRefresh();
         }
 
         super.onStart();