core: NewResourceConfigShimmed not to crash without schema
core: NewResourceConfigShimmed not to crash without schema

Although there isn't really a good reason why there should be no schema
in practice, it's better for us not to crash right now while we're still
updating all of the callers (mostly tests) to make schema available.

brandontosch/terraform,iljaskevic/terraform,tpounds/terraform,brandontosch/terraform,VladRassokhin/terraform,iljaskevic/terraform,gechr/terraform,youhong316/terraform,rnaveiras/terraform,apparentlymart/terraform,pdecat/terraform,pradeepbhadani/terraform,pdecat/terraform,apparentlymart/terraform,heimweh/terraform,heimweh/terraform,tpounds/terraform,mattray/terraform,brandontosch/terraform,nlamirault/terraform,ewbankkit/terraform,nlamirault/terraform,pryorda/terraform,ewbankkit/terraform,drebes/terraform,gechr/terraform,tommynsong/terraform,rnaveiras/terraform,luis-silva/terraform,heimweh/terraform,mattray/terraform,hashicorp/terraform,drebes/terraform,tpounds/terraform,youhong316/terraform,rnaveiras/terraform,VladRassokhin/terraform,tommynsong/terraform,drebes/terraform,nlamirault/terraform,VladRassokhin/terraform,gechr/terraform,pradeepbhadani/terraform,pryorda/terraform,ewbankkit/terraform,hashicorp/terraform,youhong316/terraform,pdecat/terraform,luis-silva/terraform,apparentlymart/terraform,iljaskevic/terraform,pradeepbhadani/terraform,iljaskevic/terraform,brandontosch/terraform,pryorda/terraform,mattray/terraform,drebes/terraform,pdecat/terraform,apparentlymart/terraform,heimweh/terraform,hashicorp/terraform,tpounds/terraform,tommynsong/terraform,apparentlymart/terraform,youhong316/terraform,brandontosch/terraform,mattray/terraform,luis-silva/terraform,ewbankkit/terraform,luis-silva/terraform,VladRassokhin/terraform,heimweh/terraform