[orca] Sanity-check offsets before calling getRangeExtents()

[Joanmarie Diggs <joanied src gnome org>]

commit 9d34ea156d33e1f44604bc376144d75ea055301c
Author: Joanmarie Diggs <jdiggs igalia com>
Date:   Mon Oct 15 16:06:46 2018 +0200

    Sanity-check offsets before calling getRangeExtents()

 src/orca/scripts/web/script_utilities.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/orca/scripts/web/script_utilities.py b/src/orca/scripts/web/script_utilities.py
index 48768009f..d66f6f944 100644
--- a/src/orca/scripts/web/script_utilities.py
+++ b/src/orca/scripts/web/script_utilities.py
@@ -717,7 +717,7 @@ class Utilities(script_utilities.Utilities):
 
         try:
             text = obj.queryText()
-            if text.characterCount:
+            if text.characterCount and 0 <= startOffset < endOffset:
                 return list(text.getRangeExtents(startOffset, endOffset, 0))
         except NotImplementedError:
             pass