[orca] Handle dead start object in _getSubtree

[Joanmarie Diggs <joanied src gnome org>]

commit a8862d2663a8668be5b80b3115063d7d50112a64
Author: Joanmarie Diggs <jdiggs igalia com>
Date:   Tue Apr 12 17:52:06 2022 +0200

    Handle dead start object in _getSubtree

 src/orca/script_utilities.py | 5 +++++
 1 file changed, 5 insertions(+)
---
diff --git a/src/orca/script_utilities.py b/src/orca/script_utilities.py
index ca0407153..7674fd978 100644
--- a/src/orca/script_utilities.py
+++ b/src/orca/script_utilities.py
@@ -5972,6 +5972,11 @@ class Utilities:
         if not (startObj and endObj):
             return []
 
+        if self.isDead(startObj):
+            msg = "INFO: Cannot get subtree: Start object is dead."
+            debug.println(debug.LEVEL_INFO, msg, True)
+            return []
+
         _include = lambda x: x
         _exclude = self.isStaticTextLeaf