[orca] Fix traceback which can occur if there's no caret context

[Joanmarie Diggs <joanied src gnome org>]

commit a4185773973c61226c4fa1780bcf8b25e01e06d9
Author: Joanmarie Diggs <jdiggs igalia com>
Date:   Mon Jul 13 20:10:41 2015 +0200

    Fix traceback which can occur if there's no caret context

 src/orca/structural_navigation.py |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/orca/structural_navigation.py b/src/orca/structural_navigation.py
index 2cff96f..7e5be1a 100644
--- a/src/orca/structural_navigation.py
+++ b/src/orca/structural_navigation.py
@@ -891,7 +891,7 @@ class StructuralNavigation:
 
         if not obj:
             obj, offset = self._script.utilities.getCaretContext()
-        thisObj, index = _getMatchingObjAndIndex(obj or currentObject)
+        thisObj, index = _getMatchingObjAndIndex(obj)
         if thisObj:
             matches = matches[index:]
             obj = thisObj