Avoid NPE when prefix is not in package cache (due to unboxing null).
Avoid NPE when prefix is not in package cache (due to unboxing null).

blue-systems-group/project.maybe.polyglot,blue-systems-group/project.maybe.polyglot,liujed/polyglot-eclipse,xcv58/polyglot,liujed/polyglot-eclipse,blue-systems-group/project.maybe.polyglot,liujed/polyglot-eclipse,blue-systems-group/project.maybe.polyglot,liujed/polyglot-eclipse,xcv58/polyglot,xcv58/polyglot,xcv58/polyglot