fixes job invoke when no build parameters exist for a particular job
fixes job invoke when no build parameters exist for a particular job

JohnLZeller/jenkinsapi,salimfadhley/jenkinsapi,jduan/jenkinsapi,jduan/jenkinsapi,imsardine/jenkinsapi,domenkozar/jenkinsapi,mistermocha/jenkinsapi,JohnLZeller/jenkinsapi,domenkozar/jenkinsapi,zaro0508/jenkinsapi,imsardine/jenkinsapi,zaro0508/jenkinsapi,imsardine/jenkinsapi,salimfadhley/jenkinsapi,JohnLZeller/jenkinsapi,aerickson/jenkinsapi,mistermocha/jenkinsapi,zaro0508/jenkinsapi,mistermocha/jenkinsapi,aerickson/jenkinsapi