ENYO-3848: fix plugin bad instanciation if it has never been instancied once before

Related JIRA: https://enyojs.atlassian.net/browse/ENYO-3848

fix plugin bad instanciation if it has never been instancied once before

Enyo-DCO-1.1-Signed-off-by: Vincent HERILIER vincent.herilier@hp.com