Properly mark free a block when coalescing is not activated.

src/custom_free.c

@@ -86,10 +86,11 @@ void custom_ahfree(allocator_t *allocator, heap_t* heap, void *ptr) {
             } else {
                 mark_free(ptr);
             }
-
         }
     } else {
+#endif /* COALESCING_FIXED || COALESCING_VARIABLE */
         mark_free(ptr);
+#if defined (COALESCING_FIXED) || defined (COALESCING_VARIABLE)
     }
 #endif /* COALESCING_FIXED || COALESCING_VARIABLE */