avoid an assert in wxString::GetWriteBuf()

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@14727 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/regconf.cpp

@@ -350,6 +350,8 @@ void wxRegConfig::SetPath(const wxString& strPath)
 
     // registry APIs want backslashes instead of slashes
     wxString strRegPath;
+    if ( !m_strPath.empty() )
+    {
         size_t len = m_strPath.length();
 
         const wxChar *src = m_strPath.c_str();
@@ -365,6 +367,7 @@ void wxRegConfig::SetPath(const wxString& strPath)
         }
 
         strRegPath.UngetWriteBuf(len);
+    }
 
     // this is not needed any longer as we don't create keys unnecessarily any
     // more (now it is done on demand, i.e. only when they're going to contain