Fix iterator traversal order

base_string.cpp

@@ -147,14 +147,12 @@ struct String_Builder {
     U64 di;
 
     void reset() {
-        for (;;) {
+        for (; first;) {
             auto *block = first;
             first = first->next;
 
             block->next = first_free;
             first_free = block;
-
-            if (!first) break;
         }
 
         last = 0;