patch 7.4.1664

Problem:    Crash in :cgetexpr.
Solution:   Check for NULL pointer. (Dominique) Add a test.

src/quickfix.c

@@ -532,7 +532,8 @@ qf_init_ext(
 		else if (tv->v_type == VAR_LIST)
 		{
 		    /* Get the next line from the supplied list */
-		    while (p_li && p_li->li_tv.v_type != VAR_STRING)
+		    while (p_li && (p_li->li_tv.v_type != VAR_STRING
+				|| p_li->li_tv.vval.v_string == NULL))
 			p_li = p_li->li_next;	/* Skip non-string items */
 
 		    if (!p_li)			/* End of the list */

src/testdir/test_quickfix.vim

@@ -692,3 +692,8 @@ func Test_caddbuffer_to_empty()
   endtry
   quit!
 endfunc
+
+func Test_cgetexpr_works()
+  " this must not crash Vim
+  cgetexpr [$x]
+endfunc

src/version.c

@@ -748,6 +748,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1664,
 /**/
     1663,
 /**/