[orca] Add check for dead accessibles before attempting to generate presentation

[Joanmarie Diggs <joanied src gnome org>]

commit ee4e53184e2deb15140cbe2a32887e160aa300c2
Author: Joanmarie Diggs <jdiggs igalia com>
Date:   Sat Apr 29 11:28:17 2017 -0400

    Add check for dead accessibles before attempting to generate presentation

 src/orca/generator.py |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/src/orca/generator.py b/src/orca/generator.py
index 1da2281..08f498b 100644
--- a/src/orca/generator.py
+++ b/src/orca/generator.py
@@ -181,6 +181,12 @@ class Generator:
         - forceTutorial: boolean (default=False) which says if we
           should force a tutorial to be spoken or not
         """
+
+        if self._script.utilities.isDead(obj):
+            msg = 'ERROR: Cannot generate presentation dead obj'
+            debug.println(debug.LEVEL_INFO, msg, True)
+            return []
+
         startTime = time.time()
         result = []
         globalsDict = {}