fix(core): throw Error when `forRoot` call is missing (#1604)
fix(core): throw Error when `forRoot` call is missing (#1604)


ngx-formly/ngx-formly,formly-js/ng-formly,formly-js/ng-formly,ngx-formly/ngx-formly,ngx-formly/ngx-formly,formly-js/ng2-formly,ngx-formly/ngx-formly,formly-js/ng2-formly,formly-js/ng2-formly