patch 9.0.0234: cannot make difference between :normal end and argument char

Problem:    Cannot make difference between the end of :normal and a character
            in its argument.
Solution:   Add the "typebuf_was_empty" flag. (closes #10950)
diff --git a/src/normal.c b/src/normal.c
index b1335a0..0ce0d4e 100644
--- a/src/normal.c
+++ b/src/normal.c
@@ -6808,11 +6808,11 @@
 #endif
     }
 #ifdef FEAT_CMDWIN
-    else if (cmdwin_type != 0 && ex_normal_busy)
+    else if (cmdwin_type != 0 && ex_normal_busy && typebuf_was_empty)
     {
 	// When :normal runs out of characters while in the command line window
-	// vgetorpeek() will return ESC.  Exit the cmdline window to break the
-	// loop.
+	// vgetorpeek() will repeatedly return ESC.  Exit the cmdline window to
+	// break the loop.
 	cmdwin_result = K_IGNORE;
 	return;
     }