grdimage [ERROR]: Option -Q: Cannot specify a transparent color for grids when intensities are also used

[vjpbd]

Description of the problem

In GMT 6.4.0 and earlier, I could use the -Q option at the same time as intensities in the module grdimage.
Since GMT 6.5.0, this doesn't work anymore.

Script that generated the error

(Modern mode, Bash script)

gmt makecpt -T-1/1 -Cgray
gmt grdimage $dem_shade
gmt makecpt -C$cpt $cpt_range
gmt grdimage $img -I$dem_shade -nn+a -Q

Full error message

grdimage [ERROR]: Option -Q: Cannot specify a transparent color for grids when intensities are also used

Expected outcome

I use this code to plot a grid, shaded with intensity, over a shaded DEM.
The grid contain NaN values and the projection is Lambert.
In version 6.4.0 and earlier, I get the following result:

Actual outcome

In version 6.5.0, I have to remove the -Q option and I get the following result:

System information

• Operating system: Debian Bullseye
• GMT version: 6.5.0

[joa-quim]

Can you make a reproducible example. A small one without unnecessary details an no variable? Just plain commands that can be copy-pasted on Windows.

[vjpbd]

Hello @joa-quim
Here is an archive with a minimal example (script, input files and results):
example.tar.gz