Fix regressions in style manager

src/style_manager/view/PropertyStackView.js

@@ -110,7 +110,8 @@ define(['backbone','./PropertyCompositeView', 'text!./../templates/propertyStack
 
       // If detached the value in this case is stacked, eg. substack-prop: 1px, 2px, 3px...
       if (this.model.get('detached')) {
-        var valist = propView.getTargetValue().split(',');
+        var targetValue = propView.getTargetValue();
+        var valist = (targetValue + '').split(',');
         result = valist[layerIndex];
         result = result ? result.trim() : propView.getDefaultValue();
         result = propView.tryFetchFromFunction(result);

test/specs/style_manager/model/Models.js

@@ -668,6 +668,7 @@ define([path + 'Sector',
               properties  : [{
                       property: 'background-image',
                       type: 'file',
+                      functionName: 'url',
                       defaults: 'none',
                     },{
                       property: 'background-repeat',

test/specs/style_manager/view/PropertyStackView.js

@@ -345,4 +345,4 @@ define([path + 'PropertyStackView', 'StyleManager/model/Property', 'DomComponent
       }
     };
 
-});
+});