patch 9.1.0713: Newline causes E749 in Ex mode

Problem:  Newline causes E749 in Ex mode (after 9.1.0573).
Solution: Don't execute empty command followed by a newline.

closes: #15614

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index 2a59301..0e69d5c 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -2916,6 +2916,11 @@
 	    }
 	    return FAIL;
 	}
+	if (eap->nextcmd == NULL && *eap->cmd == '\n')
+	{
+	    eap->nextcmd = eap->cmd + 1;
+	    return FAIL;
+	}
 	if (*eap->cmd == NUL)
 	{
 	    if (!skip_only)