prevent attaching same click event multiple times
prevent attaching same click event multiple times

andrewyatz/public-plugins,Ensembl/public-plugins,muffato/public-plugins,muffato/public-plugins,muffato/public-plugins,andrewyatz/public-plugins,andrewyatz/public-plugins,andrewyatz/public-plugins,Ensembl/public-plugins,andrewyatz/public-plugins,muffato/public-plugins,Ensembl/public-plugins