Micro optimization in wxInternetFSHandler::OpenFile()

Avoid copying the content type string unnecessarily and avoid even
calling GetContentType() in the first place in case of an error.

src/common/fs_inet.cpp

@@ -105,7 +105,6 @@ wxFSFile* wxInternetFSHandler::OpenFile(wxFileSystem& WXUNUSED(fs),
     if (url.GetError() == wxURL_NOERR)
     {
         wxInputStream *s = url.GetInputStream();
-        wxString content = url.GetProtocol().GetContentType();
         if (s)
         {
             wxString tmpfile =
@@ -120,6 +119,7 @@ wxFSFile* wxInternetFSHandler::OpenFile(wxFileSystem& WXUNUSED(fs),
             // Content-Type header, as defined by the RFC 2045, has the form of
             // "type/subtype" optionally followed by (multiple) "; parameter"
             // and we need just the MIME type here.
+            const wxString& content = url.GetProtocol().GetContentType();
             wxString mimetype = content.BeforeFirst(';');
             mimetype.Trim();