dojo.addClass: check if classStr provided

[Les]

I noticed that dojo.addClass, removeClass... don't check if the classStr parameter was provided.

If, for example, I add an undefined classStr to a tree icon node, the iconNode.className property will appear as "dijitInline dijitTreeIcon TreeIconReport? undefined".

I think, it would be better if in this example the 'undefined' class name was not added.

[bill]

I've noticed this too but it seems like a bug in the Tree code. Isn't calling dojo.addClass() without a class an error? It's not an optional parameter.

[Les]

This would happen if the user overridden functions getIconClass() or getLabelClass() didn't return a value (class string). So perhaps the Tree code could be modified to compensate for the lack of returned value in these functions, see below:

this._iconClass = tree.getIconClass(item, this.isExpanded) || '';
this._labelClass = tree.getLabelClass(item, this.isExpanded) || '';

[bill]

(In [16504]) Don't pass null or undefined argument to addClass(). Refs #8517 !strict.

[dante]

classStr is a required parameter. The developer should ensure defined values are being passed, as bill handled in [16504]. I don't think the extra few bytes in base would be worthwhile here, but please reopen if strongly opposed.