Pressing enter at direct connect with an empty server address field will result in Minecraft trying to connect to a non-existing one (the empty ip). This isn't an issue in 1.12.2.
Pressing enter on direct connect when text box is empty still attempts to connect
UI text fields that aren't supposed to be left blank by the player can be bypassed
It is possible to create a server in the server list with a blank name and/or IP address
Cannot press Enter on Direct Connect
Entering only colons into multiplayer Direct Connection & pressing enter crashes the game