Fix empty window after reconnect

Sometimes after a reconnect the current window would get cleared. This
was a deliberate change to fix the profanity window looking all garbled
up after providing the passphrase for a gpg key using pinentry-curses.

Fixes https://github.com/profanity-im/profanity/issues/1556

tests/unittests/ui/stub_ui.c

@@ -1367,6 +1367,10 @@ void
 win_clear(ProfWin* window)
 {
 }
+void
+win_redraw(ProfWin* window)
+{
+}
 char*
 win_to_string(ProfWin* window)
 {