Can happen quite often if users don't know that they have to click on the plugin first before they see the plugin documentation.
I am not sure what is exactly done here to reproduce. To get any help page I have to click on a plugin anyway. How would I provoke a blank page?
When I use F1 while the Standard Display is activated I get a blank page for the Standard Display. If that's what is meant than we need to reconsider how to display this specific help page: There is a description of the "four window view" inside src\Plugins\org.mitk.gui.qt.ext\documentation\UserManual\MITKUserManual.dox but we can not move it to the stdmultiwidgeteditor-plugin as it contains more information about the workbench, not only about the standard display.
There are other plugins / widgets that do not provide a help page, e.g. the help plugins :D
We should discuss how we want to handle non-existent help pages.