Allow ImportDeclaration kind to be undefined.
Allow ImportDeclaration kind to be undefined.

For example, given `import "foo";` the `kind` property of that node will be `undefined`.

cpojer/ast-types,benjamn/ast-types,gabelevi/ast-types,jamestalmage/ast-types,benjamn/ast-types,benjamn/ast-types,marcioj/ast-types