Fix handling of synth-tree URLs w/ empty version.
Fix handling of synth-tree URLs w/ empty version.

This ensures that a URL like this will work (shows Opisthokonta):
http:739241a16c99f1c3d3419b95c2c4f4e5f22c605f@ott332573

OpenTreeOfLife/opentree,OpenTreeOfLife/opentree,OpenTreeOfLife/opentree,OpenTreeOfLife/opentree,OpenTreeOfLife/opentree,OpenTreeOfLife/opentree