[gtk+] Avoid an out-of-bounds access

[Matthias Clasen <matthiasc src gnome org>]

commit ca3d87ce70e1a9c00a37d40eb0d8039d92368a1d
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Feb 26 15:50:31 2016 -0500

    Avoid an out-of-bounds access
    
    When the offset gets smaller than min_offset, we can't
    access the array at that position.

 gtk/gtktextiter.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)
---
diff --git a/gtk/gtktextiter.c b/gtk/gtktextiter.c
index dc3891a..3e2e5f5 100644
--- a/gtk/gtktextiter.c
+++ b/gtk/gtktextiter.c
@@ -3073,9 +3073,12 @@ inside_sentence_func (const PangoLogAttr *attrs,
                       gint                len)
 {
   /* Find next sentence start or end */
-  while (offset >= min_offset &&
-         !(attrs[offset].is_sentence_start || attrs[offset].is_sentence_end))
-    --offset;
+  while (!(attrs[offset].is_sentence_start || attrs[offset].is_sentence_end))
+    {
+      --offset;
+      if (offset < min_offset)
+        return FALSE;
+    }
 
   return attrs[offset].is_sentence_start;
 }