Q:

Prestashop 1.7 Dispatcher ContextErrorException

I have error and have no idea form is this: 
(I move prestashop form one to another server, I check php version - is the same)

A:

Because there is a warning before, the header containing the file type is already sent, then PHP cannot modify it. 
It's actually not supposed to happen on that file ... You might check this one from the sources or disable warnings/strict PHP mode.