Cannot use backspace under some circumstances

Steps to reproduce:

1) Open the multiplayer menu
2) Click "Add a server"
3) Write in server address field something like
"t.test" (a letter, a dot and another word)
4) Move the cursor to "t"
5) Try to delete "t"

What I expeted:
"t" gets deleted

What actually happen:
"t" remains as I didn't press backspace.