This assertion (for i#116192) is actually triggered while loading
fdo65932.html in CppunitTest_sw_filters_test:

The perverted LoadHiddenDocument() hack in SwHTMLParser::SetControlSize()
may create a view too early, before loading finishes, but this
shouldn't be a problem because HTML is never a template, so move the
assertion into the place where we actually modify the document directly
without going via the shell.

Change-Id: Ifa4b1ec4ab4142f4159daf5785cd90b5468f7e3e