WebRTC: Fix potential nullptr dereference in error message

This was evidently a typo. Didn't get a crash but GCC 12 raised a
`-Warray-bounds` warning:

```
In file included from ./core/io/stream_peer.h:34,
                 from ./core/io/packet_peer.h:34,
                 from ./core/multiplayer/multiplayer_peer.h:34,
                 from modules/webrtc/webrtc_multiplayer_peer.h:34,
                 from modules/webrtc/webrtc_multiplayer_peer.cpp:31:
In member function 'T* Ref<T>::operator->() [with T = WebRTCMultiplayerPeer::ConnectedPeer]',
    inlined from 'virtual Error WebRTCMultiplayerPeer::put_packet(const uint8_t*, int)' at modules/webrtc/webrtc_multiplayer_peer.cpp:376:4:
./core/object/ref_counted.h:101:24: error: array subscript 0 is outside array bounds of 'Ref<WebRTCMultiplayerPeer::ConnectedPeer> [0]' [-Werror=array-bounds]
  101 |                 return reference;
      |                        ^~~~~~~~~
```

0 files changed, 0 insertions, 0 deletions