patch 9.1.0473: term_start() does not clear vertical modifier

Problem:  term_start() does not clear vertical modifier
Solution: Clear the flag after splitting the window
          (Yegappan Lakshmanan)

closes: #14953

Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/terminal.c b/src/terminal.c
index 25a6a5d..28e1abf 100644
--- a/src/terminal.c
+++ b/src/terminal.c
@@ -538,9 +538,15 @@
 	    split_ea.addr_count = 1;
 	}
 
+	int cmod_split_modified = FALSE;
 	if (vertical)
+	{
 	    cmdmod.cmod_split |= WSP_VERT;
+	    cmod_split_modified = TRUE;
+	}
 	ex_splitview(&split_ea);
+	if (vertical && cmod_split_modified)
+	    cmdmod.cmod_split &= ~WSP_VERT;
 	if (curwin == old_curwin)
 	{
 	    // split failed