Update Proxy.java - When teleporting into unloaded chunk

Occasionally, when teleporting about, I will teleport into an unloaded chunk (or what I assume is an unloaded chunk) and I must re log into the world to loaded it up.
What makes me think this is an unloaded chunk, is that when I teleport, nothing is loaded around me. All I can see is the horizon, and I am unable to move (moving the mouse puts the screen back at the rotation it was before moving)

This PR SHOULD fix that issue. Hopefully it is valid for your liking. :)

Changelog:
   Makes sure the the destination chunk is loaded before teleporting