Isolate monkey-patched dropDownClass in createNavBox (#1439)
Isolate monkey-patched dropDownClass in createNavBox (#1439)

If createNavBox was executed multiple times, the last instance would call thisB.navigateTo on every previous instance.
GMOD/jbrowse,GMOD/jbrowse,GMOD/jbrowse,GMOD/jbrowse,GMOD/jbrowse