[orca] Add some sanity checking to handle dead accessibles from Evolution

[Joanmarie Diggs <joanied src gnome org>]

commit 71a5316be4eff37767eae1b7f294083f5af56198
Author: Joanmarie Diggs <jdiggs igalia com>
Date:   Wed Jan 21 12:48:25 2015 -0500

    Add some sanity checking to handle dead accessibles from Evolution

 src/orca/script_utilities.py                       |    6 ++++--
 .../scripts/apps/evolution/braille_generator.py    |    2 +-
 2 files changed, 5 insertions(+), 3 deletions(-)
---
diff --git a/src/orca/script_utilities.py b/src/orca/script_utilities.py
index dc62c0d..0b37080 100644
--- a/src/orca/script_utilities.py
+++ b/src/orca/script_utilities.py
@@ -295,6 +295,8 @@ class Utilities:
         #
         for i in range(row+1, table.nRows):
             cell = table.getAccessibleAt(i, col)
+            if not cell:
+                continue
             relations = cell.getRelationSet()
             for relation in relations:
                 if relation.getRelationType() \
@@ -2837,14 +2839,14 @@ class Utilities:
 
     def coordinatesForCell(self, obj):
         if not (obj and obj.getRole() == pyatspi.ROLE_TABLE_CELL):
-            return None
+            return -1, -1
 
         isTable = lambda x: x and 'Table' in pyatspi.listInterfaces(x)
         parent = pyatspi.findAncestor(obj, isTable)
         try:
             table = parent.queryTable()
         except:
-            return None
+            return -1, -1
 
         index = self.cellIndex(obj)
         return table.getRowAtIndex(index), table.getColumnHeader(index)
diff --git a/src/orca/scripts/apps/evolution/braille_generator.py 
b/src/orca/scripts/apps/evolution/braille_generator.py
index 56f7b1d..fccf795 100644
--- a/src/orca/scripts/apps/evolution/braille_generator.py
+++ b/src/orca/scripts/apps/evolution/braille_generator.py
@@ -55,7 +55,7 @@ class BrailleGenerator(WebKitGtk.BrailleGenerator):
         result, focusedRegion = super().generateBraille(obj, **args)
         self._cache = {}
 
-        if focusedRegion != result[0]:
+        if not result or focusedRegion != result[0]:
             return [result, focusedRegion]
 
         hasObj = lambda x: isinstance(x, (braille.Component, braille.Text))