Prevent crash

app/src/main/java/eu/faircode/email/FragmentBase.java

@@ -353,7 +353,9 @@ public class FragmentBase extends Fragment {
                     View custom = actionbar.getCustomView();
                     TextView tvTitle = custom.findViewById(R.id.title);
                     TextView tvSubtitle = custom.findViewById(R.id.subtitle);
+                    if (tvTitle != null)
                         tvTitle.setText(title == null ? getString(R.string.app_name) : title);
+                    if (tvSubtitle != null)
                         tvSubtitle.setText(subtitle);
                 }
         }