Fix spurious error message when plugins passed to girder-install web
Fix spurious error message when plugins passed to girder-install web

RafaelPalomar/girder,data-exp-lab/girder,adsorensen/girder,kotfic/girder,jbeezley/girder,Kitware/girder,RafaelPalomar/girder,manthey/girder,Kitware/girder,girder/girder,girder/girder,Xarthisius/girder,kotfic/girder,jbeezley/girder,RafaelPalomar/girder,manthey/girder,jbeezley/girder,data-exp-lab/girder,kotfic/girder,jbeezley/girder,kotfic/girder,RafaelPalomar/girder,sutartmelson/girder,adsorensen/girder,sutartmelson/girder,kotfic/girder,sutartmelson/girder,Xarthisius/girder,RafaelPalomar/girder,girder/girder,Kitware/girder,sutartmelson/girder,Xarthisius/girder,Xarthisius/girder,data-exp-lab/girder,manthey/girder,data-exp-lab/girder,manthey/girder,Kitware/girder,data-exp-lab/girder,adsorensen/girder,adsorensen/girder,adsorensen/girder,girder/girder,sutartmelson/girder,Xarthisius/girder