curses: assert get_wch return value is okay

This prevents the compiler from reporting a possible uninitialized use
of maybe_keycode in function curses_refresh.

Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1563451264-46176-1-git-send-email-pbonzini@redhat.com

[ kraxel: whitespace fixup ]

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

ui/curses.c

@@ -225,6 +225,8 @@ static wint_t console_getch(enum maybe_keycode *maybe_keycode)
     case ERR:
         ret = -1;
         break;
+    default:
+        abort();
     }
     return ret;
 }