Fix display of empty wxStaticBoxSizers.

wxStaticBoxSizer should be considered shown if its static box is shown, even
if it has no elements (or all of them are hidden).

Closes #14698.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73729 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Add wxDocManager::FindDocumentByPath() helper.

Simply refactor the code which already existed inside wxDocManager in a new
public method.

Closes #15126.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73730 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Fix assert when constructing invalid wxGBSpan inside wxWidgets itself.

Various wxGridBagSizer methods returning wxGBSpan asserted when trying to
construct an invalid wxGBSpan as its components must now (since r66964) be
positive.

Fix this by adding a special new method to wxGBSpan for constructing such
invalid spans and use it now.

Closes #15124.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73731 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775