bug#33990: 27.0.50; image-transform-fit-to-height/-width violates assert

[Eli Zaretskii]

> From: Benjamin Riefenstahl <b.riefenstahl@turtle-trading.net>
> Date: Sat, 05 Jan 2019 18:26:06 +0100
> 
> When I resize images, using image-transform-fit-to-height or
> image-transform-fit-to-width, the scaling is performed but than
> image-transform-check-size is called and signals an error.  This uses
> ImageMagick 6.9.7.4 as installed by Debian GNUS/Linux 9.6 (stretch).

Please show the error message and the Lisp backtrace from the error,
and also the values of the relevant variables.

Thanks.