[orca] Root must be both showing and visible before looking for descendant at point

[Joanmarie Diggs <joanied src gnome org>]

commit 3806fcc507006e331e47f11987950e6851fc5d1b
Author: Joanmarie Diggs <jdiggs igalia com>
Date:   Mon Jul 15 10:48:28 2019 -0400

    Root must be both showing and visible before looking for descendant at point

 src/orca/script_utilities.py | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/src/orca/script_utilities.py b/src/orca/script_utilities.py
index 60407f7ac..143a630d4 100644
--- a/src/orca/script_utilities.py
+++ b/src/orca/script_utilities.py
@@ -4055,6 +4055,9 @@ class Utilities:
         if not root:
             return None
 
+        if not self.isShowingAndVisible(root):
+            return None
+
         if coordType is None:
             coordType = pyatspi.DESKTOP_COORDS