return immediately from WalkFrom() if dbghelp dll initialization fails (part of patch 1212925)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@34497 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/stackwalk.cpp

@@ -220,6 +220,7 @@ void wxStackWalker::WalkFrom(const CONTEXT *pCtx, size_t skip)
     {
         wxLogError(_("Failed to get stack backtrace:\n%s"),
                    wxDbgHelpDLL::GetErrorMessage().c_str());
+        return;
     }
 
     // according to MSDN, the first parameter should be just a unique value and