[orca] Fix for bgo#618801 - Traceback in Thunderbird

[Joanmarie Diggs <joanied src gnome org>]

commit 37effc4bd539d5c694ac16f39219d1b4df73af46
Author: Joanmarie Diggs <joanmarie diggs gmail com>
Date:   Sun May 16 13:53:16 2010 -0400

    Fix for bgo#618801 - Traceback in Thunderbird

 src/orca/scripts/apps/Thunderbird/script.py |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/src/orca/scripts/apps/Thunderbird/script.py b/src/orca/scripts/apps/Thunderbird/script.py
index 8d2087f..0fedbea 100644
--- a/src/orca/scripts/apps/Thunderbird/script.py
+++ b/src/orca/scripts/apps/Thunderbird/script.py
@@ -394,7 +394,8 @@ class Script(Gecko.Script):
                      pyatspi.ROLE_SCROLL_PANE,
                      pyatspi.ROLE_SCROLL_PANE]
         if self.utilities.hasMatchingHierarchy(event.source, rolesList):
-            if isinstance(orca_state.lastInputEvent, input_event.KeyboardEvent):
+            if isinstance(orca_state.lastInputEvent, input_event.KeyboardEvent)\
+               and orca_state.lastNonModifierKeyEvent:
                 string = orca_state.lastNonModifierKeyEvent.event_string
                 if string == "Delete":
                     oldLocusOfFocus = None