OptionSet -Error appears when 'upload' button in the ImageSelector was pressed

[sgauruseu]

-This bug reproduced, when there is the next level of nesting of OptionSet:
content-type->mixin->item-set->item-set->option-set->mixin->option-set->input[type=ImageSelector]
-Probably, the cause of this issue the mixin inside of optionset:
inline mixin="freeform-input-types"
this mixin contains an ImageSelector. Error does not appear when the mixin replaced with ImageSelector

-The similar issue when AttachmentUploader present in the nested optionSet

1. create two mixins with name freeform and freeform-input-types
2. create a content type 'FreeForm'
3. start to create a content with type
4. click on the image radio button and try to upload an image
   BUG: Upload dialog does not appear , error in the console
   Uncaught TypeError: Cannot read property 'getInputButton' of undefined
   at ImageUploaderEl.UploaderEl.showFileSelectionDialog (_all.js:20191)
   at HTMLDivElement. (_all.js:19653)