[orca] Mouse Review: Gracefully handle lack of pointer

[Joanmarie Diggs <joanied src gnome org>]

commit aa98ef4ba069f9c26607e2af840e71cfb5429dc5
Author: Joanmarie Diggs <jdiggs igalia com>
Date:   Mon Jun 28 10:56:57 2021 +0200

    Mouse Review: Gracefully handle lack of pointer
    
    Apparently in some environments getting the pointer from the default seat
    of the GDK display returns null rather than errors out. Handle this error.

 src/orca/mouse_review.py | 5 +++++
 1 file changed, 5 insertions(+)
---
diff --git a/src/orca/mouse_review.py b/src/orca/mouse_review.py
index 6f1d53b8f..967f5de25 100644
--- a/src/orca/mouse_review.py
+++ b/src/orca/mouse_review.py
@@ -347,6 +347,11 @@ class MouseReviewer:
             debug.println(debug.LEVEL_INFO, msg, True)
             return
 
+        if not self._pointer:
+            msg = "MOUSE REVIEW ERROR: No pointer for default seat."
+            debug.println(debug.LEVEL_INFO, msg, True)
+            return
+
         if not self._active:
             return