[gjs] tweener: Add undefined property check

[Philip Chimento <pchimento src gnome org>]

commit e606a06ecbfaf29d23b37d81851c125f077f20a8
Author: Philip Chimento <philip chimento gmail com>
Date:   Sun May 21 20:45:59 2017 -0700

    tweener: Add undefined property check
    
    To avoid a rare SpiderMonkey warning. Unreviewed.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=781219

 modules/tweener/tweener.js |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/modules/tweener/tweener.js b/modules/tweener/tweener.js
index 83bc870..e0e48d9 100644
--- a/modules/tweener/tweener.js
+++ b/modules/tweener/tweener.js
@@ -535,7 +535,7 @@ function _addTweenOrCaller(target, tweeningParameters, isCaller) {
                 copyProperties[istr] = new PropertyInfo(properties[istr].valueStart,
                                                         properties[istr].valueComplete,
                                                         properties[istr].valueComplete,
-                                                        properties[istr].arrayIndex,
+                                                        properties[istr].arrayIndex || 0,
                                                         {},
                                                         properties[istr].isSpecialProperty,
                                                         properties[istr].modifierFunction,