there are two of these GetUserData()[0] tests, use startsWith for both

Change-Id: Iacb40220a87563a53a521b35efe208bb3b90e653

sw/source/filter/basflt/iodetect.cxx

@@ -171,7 +171,7 @@ const SfxFilter* SwIoSystem::GetFileFilter(const OUString& rFileName)
             {
                 while ( pFilter )
                 {
-                    if( !pFilter->GetUserData().isEmpty() && 'C' == pFilter->GetUserData()[0] && IsValidStgFilter( xStor, *pFilter ) )
+                    if (pFilter->GetUserData().startsWith("C") && IsValidStgFilter(xStor, *pFilter ))
                     {
                         if (pFilter->IsOwnTemplateFormat())
                         {
@@ -206,7 +206,7 @@ const SfxFilter* SwIoSystem::GetFileFilter(const OUString& rFileName)
             {
                 while ( pFilter )
                 {
-                    if( 'C' == pFilter->GetUserData()[0] && IsValidStgFilter( *xStg, *pFilter ) )
+                    if (pFilter->GetUserData().startsWith("C") && IsValidStgFilter(*xStg, *pFilter))
                     {
                         if (pFilter->IsOwnTemplateFormat())
                         {