Only allow opening existing files in docview framework.

Use wxFD_FILE_MUST_EXIST when asking the user for the name of the file to
open.

Closes #11866.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@63784 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/docview.cpp

@@ -1625,7 +1625,8 @@ wxDocTemplate *wxDocManager::SelectDocumentPath(wxDocTemplate **templates,
                                         GetLastDirectory(),
                                         wxEmptyString,
                                         &FilterIndex,
-                                        descrBuf);
+                                        descrBuf,
+                                        wxFD_OPEN | wxFD_FILE_MUST_EXIST);
 
     wxDocTemplate *theTemplate = NULL;
     if (!pathTmp.empty())