[vte/vte-next] Remove a segfault when passing null in tag argument

[Christian Persch <chpe src gnome org>]

commit 70da99aaf92f260d337806692a319f4f191beb85
Author: Jacques-Pascal Deplaix <jp deplaix gmail com>
Date:   Sat May 26 17:08:56 2012 +0200

    Remove a segfault when passing null in tag argument
    
    Bug #676886.

 src/vte.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/src/vte.c b/src/vte.c
index 72eb5bf..eec9fb0 100644
--- a/src/vte.c
+++ b/src/vte.c
@@ -1649,7 +1649,9 @@ vte_view_match_check_internal_gregex(VteView *terminal,
 
 	_vte_debug_print(VTE_DEBUG_EVENTS,
 			"Checking for gregex match at (%ld,%ld).\n", row, column);
-	*tag = -1;
+	if (tag != NULL) {
+		*tag = -1;
+	}
 	if (start != NULL) {
 		*start = 0;
 	}