Fix `importName` type confusion (string, bool, node) (#233)
Fix `importName` type confusion (string, bool, node) (#233)

Apparently `importName` can have many different types:
https://github.com/styled-components/babel-plugin-styled-components/issues/232#issuecomment-507223968

This commit ensures that the check whether the name is in the scope
(bindings) does not break on plain strings.

Closes: #232
styled-components/babel-plugin-styled-components