Prevent access to FlowrSettings after page navigation

When users have a running execution and navigate away, `this.getFlowrSettings()` might be `undefined`.

Fixes CODEOCEAN-FRONTEND-DK

Author: MrSerth

app/assets/javascripts/editor/participantsupport.js

@@ -77,7 +77,7 @@ CodeOceanEditorFlowr = {
     return results;
   },
   handleStderrOutputForFlowr: function () {
-    if (! this.getFlowrSettings().enabled) return;
+    if (! this.getFlowrSettings()?.enabled) return;
 
     var flowrHintBody = $('#flowrHint .card-body');
     flowrHintBody.empty();