Add hack to work around mystery settings bug

src/components/views/settings/tabs/user/GeneralUserSettingsTab.js

@@ -185,7 +185,10 @@ export default class GeneralUserSettingsTab extends React.Component {
         // The settings watcher doesn't fire until the echo comes back from the
         // server, so to make the theme change immediately we need to manually
         // do the dispatch now
-        dis.dispatch({action: 'recheck_theme'});
+        // XXX: The local echoed value appears to be unreliable, in particular
+        // when settings custom themes(!) so adding forceTheme to override
+        // the value from settings.
+        dis.dispatch({action: 'recheck_theme', forceTheme: newTheme});
     };
 
     _onUseSystemThemeChanged = (checked) => {