[orca] Ignore children-changed:removed events with detail1 set to -1

[Joanmarie Diggs <joanied src gnome org>]

commit 9988c713b2dd7345b5c5d28f48b1ef0bf6f6e479
Author: Joanmarie Diggs <jdiggs igalia com>
Date:   Tue May 19 19:23:40 2020 -0400

    Ignore children-changed:removed events with detail1 set to -1
    
    We cannot use a useless index when attempting to recover our location.
    Apparently ancient versions of Firefox don't give us a valid index.

 src/orca/scripts/web/script_utilities.py | 5 +++++
 1 file changed, 5 insertions(+)
---
diff --git a/src/orca/scripts/web/script_utilities.py b/src/orca/scripts/web/script_utilities.py
index a67d6588c..b6012688b 100644
--- a/src/orca/scripts/web/script_utilities.py
+++ b/src/orca/scripts/web/script_utilities.py
@@ -4586,6 +4586,11 @@ class Utilities(script_utilities.Utilities):
         msg = "WEB: Removed child is locusOfFocus."
         debug.println(debug.LEVEL_INFO, msg, True)
 
+        if event.detail1 == -1:
+            msg = "WEB: Event detail1 is useless."
+            debug.println(debug.LEVEL_INFO, msg, True)
+            return False
+
         obj, offset = None, -1
         keyString, mods = self.lastKeyAndModifiers()
         if keyString == "Up":