With the new image template code, concatenation doesn't work well

[olebole]

Describe the bug

The new image template code (in sys/imio/imt/imx.x) has some bugs with concatenating with strings.

To Reproduce Steps to reproduce the behavior.

ecl> set use_vo=yes          # ensure the new code is used
ecl> set use_new_imt=yes     #           ''
ecl> imcopy dev$pix pix.fits
dev$pix -> pix.fits
ecl> files pix.fits > flist
ecl> imrename @flist new//@flist
ERROR: segmentation violation

Expected behavior

like for the old template code:

ecl> set use_new_imt=no
ecl> imrename @flist new//@flist
ecl> dir
flist        newpix.fits  

System details:

• Version 2.16.1, 2.17

Additional context

• taken from https://iraf.net/forum/viewtopic.php?showtopic=1469293 (2.16.1, still in 2.17)
• similar (but appending) https://iraf.net/forum/viewtopic.php?showtopic=1469293

There seem other mentions of this, but they partially belong to older versions.