fix: major bug in allocator

niarena.h

@@ -81,8 +81,9 @@ niarena_alloc(NIArena **self, size_t size)
 		niarena_error("niarena_alloc: out of memory inside of the arena");
 		return NULL;
 	}
+	void *ret = (void *)(((char *)arena->buffer) + arena->offset);
 	arena->offset += size;
-	return (void *)((char *)arena->buffer + arena->offset);
+	return ret;
 }
 
 void