patch 8.2.0921: CTRL-W T in cmdline window causes trouble

Problem:    CTRL-W T in cmdline window causes trouble.
Solution:   Disallow CTRL-W T in the cmdline window.  Add more tests.
            (Naruhiko Nishino, closes #6219)
diff --git a/src/window.c b/src/window.c
index 931d86b..095eabe 100644
--- a/src/window.c
+++ b/src/window.c
@@ -340,6 +340,7 @@
 
 // move window to new tab page
     case 'T':
+		CHECK_CMDWIN;
 		if (one_window())
 		    msg(_(m_onlyone));
 		else