[FIX] web: regard the view_list has valid if not yet loaded

This fix is related to df845940ed52040ef92b1b5759306c556fa38e66

Fixes #3469
[MERGE] forward port of branch 7.0 up to 9a37e5a
[MERGE] forward port of branch saas-3 up to c11451c
[FIX] ir_qweb, website_blog: Allow to pass inline style as an option for the widget image. And change some img from blog to use this widget
[IMP] models: improve _mapped_func(), and add parameter 'reverse' in sorted()
[FIX] Report: get_pdf:  don't miss main elements when parsing html

Main elements can have more than one class, thus can be ignored by the previous
naive xpath. This patch brings a stronger xpath.