[orca] Make our new _findAllDescendants() more robust against defunct objects

[Joanmarie Diggs <joanied src gnome org>]

commit 223894fe39cd537dc9962ba10fbcf0e5dbd4809e
Author: Joanmarie Diggs <jdiggs igalia com>
Date:   Wed Nov 21 10:09:30 2018 -0500

    Make our new _findAllDescendants() more robust against defunct objects
    
    * Return early if we cannot obtain the root's childCount
    * Return early if we cannot get a particular child

 src/orca/script_utilities.py | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)
---
diff --git a/src/orca/script_utilities.py b/src/orca/script_utilities.py
index 76283bc34..7b8be9116 100644
--- a/src/orca/script_utilities.py
+++ b/src/orca/script_utilities.py
@@ -2284,7 +2284,21 @@ class Utilities:
         return not (extents.width and extents.height)
 
     def _findAllDescendants(self, root, includeIf, excludeIf, matches):
-        for child in root:
+        try:
+            childCount = root.childCount
+        except:
+            msg = "ERROR: Exception getting childCount for %s" % root
+            debug.println(debug.LEVEL_INFO, msg, True)
+            return
+
+        for i in range(childCount):
+            try:
+                child = root[i]
+            except:
+                msg = "ERROR: Exception getting %i child for %s" % (i, root)
+                debug.println(debug.LEVEL_INFO, msg, True)
+                return
+
             if excludeIf and excludeIf(child):
                 continue
             if includeIf and includeIf(child):