xml2guido: Fix Single Tremolo closings
xml2guido: Fix Single Tremolo closings

dfober/libmusicxml,dfober/libmusicxml,dfober/libmusicxml,arshiacont/libmusicxml,grame-cncm/libmusicxml,arshiacont/libmusicxml,grame-cncm/libmusicxml,grame-cncm/libmusicxml,dfober/libmusicxml,grame-cncm/libmusicxml,arshiacont/libmusicxml,grame-cncm/libmusicxml,arshiacont/libmusicxml,grame-cncm/libmusicxml,arshiacont/libmusicxml