transform [:static, ""] to [:multi, [:static, ""]] in interpolation
transform [:static, ""] to [:multi, [:static, ""]] in interpolation

needed to fix #187

JuanitoFatas/slim,sideci-sample/sideci-sample-slim,raxoft/slim,Nikeshsuwal/slim,fly19890211/slim,yterajima/slim,XueQian/slim,etdev/slim,slim-template/slim,raxoft/slim,slim-template/slim,slim-template/slim,JuanitoFatas/slim,mojavelinux/slim,fly19890211/slim,etdev/slim,zakuro9715/slim,metallurgical/slim,metallurgical/slim,cheunghy/slim,ruijsun/slim,ericboehs/slim,XueQian/slim,cheunghy/slim,ericboehs/slim,Nikeshsuwal/slim,mojavelinux/slim,ruijsun/slim,zakuro9715/slim