Fix loose mode for missing import target
Fix loose mode for missing import target

Closes #409

mathiasbynens/acorn,TimothyGu/acorn,TimothyGu/acorn,MarcelGerber/acorn,ternjs/acorn,marijnh/acorn,mysticatea/acorn,mysticatea/acorn,marijnh/acorn,ternjs/acorn,TimothyGu/acorn,ajaxorg/acorn,Rich-Harris/acorn,MarcelGerber/acorn,marijnh/acorn,Rich-Harris/acorn,mathiasbynens/acorn,Rich-Harris/acorn,mathiasbynens/acorn,MarcelGerber/acorn,mysticatea/acorn,ajaxorg/acorn,ternjs/acorn,ajaxorg/acorn