When signalling json-readtable-error, the macro json-readtable-dispatch
passes the unrecognised character as error data verbatim, rather than as
a list.  Attached is a patch which fixes this.

Thanks,

-- 
Basil

In GNU Emacs 26.0.91 (build 3, x86_64-pc-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2018-02-16 built on thunk
Repository revision: edc06adf96f4aa9d8b707181015acfe61d396edb
Windowing system distributor 'The X.Org Foundation', version 11.0.11906000
System Description:	Debian GNU/Linux testing (buster)