Allow normal page scrolling over timeline (#3818)

lib/timeline/Core.js

@@ -204,9 +204,12 @@ Core.prototype._create = function (container) {
       deltaX = event.deltaX;
     }
 
-    // prevent scrolling when zoomKey defined or activated
+    // Prevent scrolling when zooming (no zoom key, or pressing zoom key)
     if (!this.options.zoomKey || event[this.options.zoomKey]) return;
 
+    // Don't preventDefault if you can't scroll
+    if (!this.options.verticalScroll && !this.options.horizontalScroll) return;
+
     // Prevent default actions caused by mouse wheel
     // (else the page and timeline both scroll)
     event.preventDefault();