Avoid warnings

Author: cloudwu

src/lua-seri.c

@@ -100,7 +100,7 @@ blk_alloc(void) {
 static inline void
 wb_push(struct write_block *b, const void *buf, int sz) {
 	const char * buffer = buf;
-	if (b->ptr == BLOCK_SIZE) {
+	if (b->ptr >= BLOCK_SIZE) {
 _again:
 		b->current = b->current->next = blk_alloc();
 		b->ptr = 0;