What are the possible errors to get this error message?
I tried to google but it says it happens in the javascript file where the getelementbyid returns null. But I checked all the element ids and they are correct... I am thinking it could be some errors regarding to the wizard section in xml.
The most fundamental cause of this error is when Javascript encounters a statement attempting to read a property through an array index that doesn't exist, eg 'someArray[0].someProperty' would throw such an error if nothing exits at array index 0 of 'someArray'.
A very typical situation in which this arises is when a function is called that normally returns an array and the code assumes the 0 index exists; this often happens in jQuery calls where so many of those selector-type functions return an array of values, and the expectation/assumption is that the desired action is to be taken against the first element (index 0).
