fix(core): avoid creation a dummy field for nested key (#2560)
fix(core): avoid creation a dummy field for nested key (#2560)

fix #2547

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