Fix error when expanding feature tracks
Fix error when expanding feature tracks

igvteam/igv.js,igvteam/igv.js,NabaviLab/CNV-Visualizer,NabaviLab/CNV-Visualizer,NabaviLab/CNV-Visualizer,NabaviLab/CNV-Visualizer,NabaviLab/CNV-Visualizer