Admin area not working anymore

Hi,
I can’t redesign a widget, here is the error:

admin.min.js:107 TypeError: Cannot set property ‘placeholder’ of null
at Object.text (admin.min.js:3294)
at Object.update (admin.min.js:3500)
at Object.fn (admin.min.js:2383)
at r.$digest (admin.min.js:131)
at r.$apply (admin.min.js:134)
at g (admin.min.js:88)
at R (admin.min.js:92)
at XMLHttpRequest.v.onload (admin.min.js:93)