[orca] Fix traceback seen when presenting a null object

[Joanmarie Diggs <joanied src gnome org>]

commit ead7b55cd3636ead726ec9ea87c49811ab84df5b
Author: Joanmarie Diggs <jdiggs igalia com>
Date:   Thu Nov 27 19:14:56 2014 -0500

    Fix traceback seen when presenting a null object

 src/orca/scripts/toolkits/Gecko/script.py          |    4 ++--
 .../toolkits/Gecko/structural_navigation.py        |    3 +++
 2 files changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/src/orca/scripts/toolkits/Gecko/script.py b/src/orca/scripts/toolkits/Gecko/script.py
index e88e6fc..17f53c1 100644
--- a/src/orca/scripts/toolkits/Gecko/script.py
+++ b/src/orca/scripts/toolkits/Gecko/script.py
@@ -2577,7 +2577,7 @@ class Script(default.Script):
 
         [obj, characterOffset] = self.getCaretContext()
         thisLine = self.getLineContentsAtOffset(obj, characterOffset)
-        if not thisLine and thisLine[0]:
+        if not (thisLine and thisLine[0]):
             return False
 
         startObj, startOffset = thisLine[0][0], thisLine[0][1]
@@ -2607,7 +2607,7 @@ class Script(default.Script):
 
         [obj, characterOffset] = self.getCaretContext()
         thisLine = self.getLineContentsAtOffset(obj, characterOffset)
-        if not thisLine and thisLine[0]:
+        if not (thisLine and thisLine[0]):
             return False
 
         lastObj, lastOffset = thisLine[-1][0], thisLine[-1][2]
diff --git a/src/orca/scripts/toolkits/Gecko/structural_navigation.py 
b/src/orca/scripts/toolkits/Gecko/structural_navigation.py
index ed518c9..7bea027 100644
--- a/src/orca/scripts/toolkits/Gecko/structural_navigation.py
+++ b/src/orca/scripts/toolkits/Gecko/structural_navigation.py
@@ -147,6 +147,9 @@ class GeckoStructuralNavigation(structural_navigation.StructuralNavigation):
     def _presentObject(self, obj, offset):
         """Presents the entire object to the user."""
 
+        if not obj:
+            return
+
         if obj.getRole() == pyatspi.ROLE_LINK:
             try:
                 obj.queryComponent().grabFocus()