Refactor _extractVocabFromExercises method for improved array handling

- Enhanced the method to better handle various input types, including array-like objects, with detailed console logging for conversion attempts and errors.
- Implemented a fallback mechanism for manual conversion of non-array inputs, ensuring robustness in vocabulary extraction.
- Updated comments for clarity on input expectations and processing logic, improving maintainability.

frontend/src/views/social/VocabLessonView.vue

@@ -412,7 +412,9 @@ export default {
         console.error('Fehler in importantVocab computed property:', e);
         return [];
       }
+    }
   },
+  methods: {
     _extractVocabFromExercises(exercises) {
       // Sicherstellen, dass exercises ein Array ist
       if (!exercises) {
@@ -420,18 +422,33 @@ export default {
         return [];
       }
       
-      // Konvertiere zu Array falls nötig
+      // Konvertiere Vue Proxy oder Objekt zu Array
       let exercisesArray = exercises;
-      if (!Array.isArray(exercises)) {
-        console.warn('[_extractVocabFromExercises] exercises ist kein Array, versuche zu konvertieren:', exercises);
-        // Falls es ein Objekt mit length ist, versuche es zu konvertieren
-        if (typeof exercises === 'object' && exercises.length !== undefined) {
+      
+      // Prüfe ob es bereits ein Array ist (auch Vue Proxy-Arrays)
+      const isArrayLike = exercises.length !== undefined && typeof exercises.length === 'number';
+      
+      if (!Array.isArray(exercises) && isArrayLike) {
+        console.log('[_extractVocabFromExercises] exercises ist kein Array, aber array-like, konvertiere...');
+        // Versuche Array.from (funktioniert mit iterierbaren Objekten und Array-like Objekten)
+        try {
           exercisesArray = Array.from(exercises);
-        } else {
-          console.error('[_extractVocabFromExercises] Kann exercises nicht zu Array konvertieren:', exercises);
+        } catch (e) {
+          // Fallback: Manuelle Konvertierung
+          try {
+            exercisesArray = [];
+            for (let i = 0; i < exercises.length; i++) {
+              exercisesArray.push(exercises[i]);
+            }
+          } catch (e2) {
+            console.error('[_extractVocabFromExercises] Kann exercises nicht zu Array konvertieren:', exercises, e2);
             return [];
           }
         }
+      } else if (!Array.isArray(exercises)) {
+        console.error('[_extractVocabFromExercises] exercises ist weder Array noch array-like:', exercises);
+        return [];
+      }
       
       const vocabMap = new Map();
       
@@ -512,9 +529,7 @@ export default {
       const result = Array.from(vocabMap.values());
       console.log(`[_extractVocabFromExercises] Ergebnis:`, result.length, 'Vokabeln');
       return result;
-    }
     },
-  watch: {
     courseId(newVal, oldVal) {
       if (newVal !== oldVal) {
         // Reset Flags beim Kurswechsel