fix get() in hash_map_chaining.c (#845)

Fix get function.

codes/c/chapter_hashing/hash_map_chaining.c

@@ -88,6 +88,7 @@ const char *get(hashMapChaining *hashmap, const int key) {
         if (node->key == key) {
             return node->val;
         }
+        node = node->next;
     }
     return NULL;
 }