When I click the Login or click the shopping cart button I get this error:

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An unknown response null: :text/html; charset=utf-8: :SyntaxError: JSON.parse: unexpected character at line 1 column 1 of the JSON data was received while processing an ajax call. The action you requested could not be completed.

I found a solution by DrByte but those changes are already installed into Sheffield Blue.

Can anyone please help me?