[chrome-gnome-shell] connector: fixed possible AttributeError

[Yuri Konotopov <ykonotopov src gnome org>]

commit 63d896692d4579a98c678d3bff5c5728d702a9fa
Author: Yuri Konotopov <ykonotopov gnome org>
Date:   Tue Mar 14 21:47:27 2017 +0400

    connector: fixed possible AttributeError

 connector/chrome-gnome-shell.py |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/connector/chrome-gnome-shell.py b/connector/chrome-gnome-shell.py
index 83110f2..4b4a07f 100755
--- a/connector/chrome-gnome-shell.py
+++ b/connector/chrome-gnome-shell.py
@@ -357,7 +357,7 @@ class ChromeGNOMEShell(Gio.Application):
             source = Gio.SettingsSchemaSource.get_default()
             shell_version = self.shell_proxy.get_cached_property("ShellVersion")
 
-            if source.lookup(SHELL_SCHEMA, True) is not None and shell_version is not None:
+            if source is not None and source.lookup(SHELL_SCHEMA, True) is not None and shell_version is not 
None:
                 settings = Gio.Settings.new(SHELL_SCHEMA)
 
                 if EXTENSION_DISABLE_VERSION_CHECK_KEY in settings.keys():