patch 9.1.1746: Missing Null ptr check in cs_find_common()

Problem:  Missing Null ptr check in cs_find_common()
Solution: Return when tmp pointer is null (ashamedbit)

fixes: #18225
closes: #18248

Signed-off-by: ashamedbit <muralianiruddhan@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

Author: ashamedbit

src/if_cscope.c

@@ -1232,6 +1232,9 @@ cs_find_common(
 	qf_info_T   *qi = NULL;
 	win_T	    *wp = NULL;
 
+	if (tmp == NULL)
+	    return FALSE;
+
 	f = mch_fopen((char *)tmp, "w");
 	if (f == NULL)
 	    semsg(_(e_cant_open_file_str), tmp);

src/version.c

@@ -724,6 +724,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1746,
 /**/
     1745,
 /**/