BUGFIX Only apply the logic for adding page type to the Pages section, n...

...ot the assets. The id for the "Create folder" button in assets is very confusingly labelled #addpage. As a result, logic intended for the cms main section was also getting applied. Commit f4b7fe05fa62 introduced a regression, and the assets folder is frozen due to a js error. I have tested that this change is fine, and that the create folder functionality is still working as intended.