corrected treeSizeRec cause previously end of non void function could be reached

bintree.c

@@ -12,7 +12,6 @@
     * `nextTreeData`: Traversierung mit Hilfe des zuvor implementierten Stacks. Done */  
 
 
-    static TreeNode     *root       = NULL;
     static StackNode    *stackRoot  = NULL;
 
 
@@ -185,5 +184,7 @@ int treeSizeRec(const TreeNode *currentNode)
         nodeCount += treeSizeRec(currentNode->right);
         return nodeCount + 1;
     }
+
+    return nodeCount;
 }