synedit: fixed range check in TSynEditMarkupGutterMark.PrepareMarkupForRow

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@42203 4005530d-fff6-0310-9dd1-cebe43e6787f
SynEdit: fixed check for max marks per line (gutter marks)

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@42204 4005530d-fff6-0310-9dd1-cebe43e6787f