Ensure arena is freed when initialisation fails

mem/src/arena/mem_arena.c

@@ -6,6 +6,8 @@
 #include <string.h>
 
 #ifndef DEFAULT_ALIGNMENT
+// Why 2 * sizeof(void *) instead of sizeof(void *)
+// https://handmade.network/forums/t/6860-alignment_arena_allocator
 #define DEFAULT_ALIGNMENT (2 * sizeof(void *))
 #endif /* ifndef DEFAULT_ALIGNMENT */
 
@@ -47,12 +49,14 @@ bool mem_arena_init(Arena **arena, u64 base_capacity) {
 
   arena_ptr->active_arena = (BaseArena *)malloc(sizeof(BaseArena));
   if (!(arena_ptr->active_arena)) {
+    mem_arena_free(arena);
     return false;
   }
 
   memset(arena_ptr->active_arena, 0, sizeof(BaseArena));
 
   if (!base_arena_init(arena_ptr->active_arena, base_capacity)) {
+    mem_arena_free(arena);
     return false;
   }