window-list: Use Infinity instead of special-casing 0

This should fix the problem addressed in the last commit without
breaking 0 as stable sequence.

extensions/window-list/extension.js

@@ -59,9 +59,8 @@ function _onMenuStateChanged(menu, isOpen) {
 
 function _getAppStableSequence(app) {
     return app.get_windows().reduce(function(prev, cur) {
-        let seq = cur.get_stable_sequence();
-        return prev ? Math.min(prev, seq) : seq;
-    }, 0);
+        return Math.min(prev, cur.get_stable_sequence());
+    }, Infinity);
 }