added guard against calling #moveForward and #moveBack in LightBox when at beginning or end of list
added guard against calling #moveForward and #moveBack in LightBox when at beginning or end of list

UCDavisLibrary/scribeAPI,HackTheDinos/crowd_saurus,UCDavisLibrary/scribeAPI,HackTheDinos/crowd_saurus,YaleDHLab/ensemble-at-yale,UCDavisLibrary/scribeAPI,zooniverse/scribeAPI,HackTheDinos/crowd_saurus,zooniverse/scribeAPI,YaleDHLab/ensemble-at-yale,YaleDHLab/ensemble-at-yale,HackTheDinos/crowd_saurus,zooniverse/scribeAPI,zooniverse/scribeAPI,HackTheDinos/crowd_saurus,UCDavisLibrary/scribeAPI,YaleDHLab/ensemble-at-yale,UCDavisLibrary/scribeAPI