Invalid free when requesting the same url twice

[krichprollsch]

Calling client.async_open twice with the same url throw a async_open error.
Full stack: https://gist.github.com/krichprollsch/383af3bb23f376534832cd1a0039f455

thread 772351 panic: Invalid free
/usr/local/zig-0.13.0/lib/std/heap/general_purpose_allocator.zig:652:21: 0x125368c in freeLarge (test)
                    @panic("Invalid free");
                    ^
/usr/local/zig-0.13.0/lib/std/heap/general_purpose_allocator.zig:840:31: 0x124ab24 in free (test)
                self.freeLarge(old_mem, log2_old_align, ret_addr);
                              ^
/usr/local/zig-0.13.0/lib/std/mem/Allocator.zig:98:28: 0x136c139 in destroy__anon_18379 (test)
    return self.vtable.free(self.ptr, buf, log2_buf_align, ret_addr);
                           ^
/home/pierre/wrk/zig-async-io/src/std/http/Client.zig:1700:43: 0x12b417a in setConnection (test)
    defer ctx.req.client.allocator.destroy(old_conn);
                                          ^
/home/pierre/wrk/zig-async-io/src/std/http/Client.zig:2460:13: 0x12506de in pop (test)
            return @call(.auto, func, .{ self, res });
            ^
/home/pierre/wrk/zig-async-io/src/std/net.zig:2008:19: 0x136c25c in onTcpConnectToHost (test)
    return ctx.pop({});
                  ^
/home/pierre/wrk/zig-async-io/src/std/http/Client.zig:2460:13: 0x12506de in pop (test)
            return @call(.auto, func, .{ self, res });
            ^