Deleted restriction of IPs
Corrected bugs

-The app crashed when the windows got closed.
-It was sending emty strings as messages
-It was possible to try to send a message to a disconnected client,
making the program crash.
-It crashed when a client disconnected from the server.
Added a feature. Corrected a bug.

-Added a method to get the IP to ConnectionServer.
-Corrected a bug that tried to delete Connections when the list was
empty.
-Fixed the crash when the widnows was closed by deleting the UI after
everything else.