Support file associations using "show" verb under MSW too.

If we failed to find the "open" command, try the "show" one as some programs
(notable Microsoft viewers for Office file formats) only define the latter but
not the former.

Closes #15821.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75606 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/mimetype.cpp

@@ -339,6 +339,11 @@ wxFileTypeImpl::GetOpenCommand(wxString *openCmd,
 {
     wxString cmd = GetCommand(wxT("open"));
 
+    // Some viewers don't define the "open" verb but do define "show" one, try
+    // to use it as a fallback.
+    if ( cmd.empty() )
+        cmd = GetCommand(wxT("show"));
+
     *openCmd = wxFileType::ExpandCommand(cmd, params);
 
     return !openCmd->empty();