Fixed consistently falling back to "bottom" orientation in case of invalid values

lib/timeline/Core.js

@@ -688,7 +688,7 @@ Core.prototype._redraw = function() {
 
   // reposition the scrollable contents
   var offset = this.props.scrollTop;
-  if (options.orientation.item == 'bottom') {
+  if (options.orientation.item != 'top') {
     offset += Math.max(this.props.centerContainer.height - this.props.center.height -
       this.props.border.top - this.props.border.bottom, 0);
   }
@@ -944,7 +944,7 @@ Core.prototype._updateScrollTop = function () {
   if (scrollTopMin != this.props.scrollTopMin) {
     // in case of bottom orientation, change the scrollTop such that the contents
     // do not move relative to the time axis at the bottom
-    if (this.options.orientation.item == 'bottom') {
+    if (this.options.orientation.item != 'top') {
       this.props.scrollTop += (scrollTopMin - this.props.scrollTopMin);
     }
     this.props.scrollTopMin = scrollTopMin;