I’ve already seen it: nextcloud is running its cron job just during the update. After the updates has been done, no more errors should be generated. So, if you do not see any errors of that kind, you can just ignore it 
@mrmarkuz I’ve tried to replicate your problem without success during and update from 7.7 to 7.8. I’ve also tested a clean 7.8 install.
I always end up with a correct ImageMagick release:
sclo-php73-php-pecl-imagick-3.4.4-3.el7.x86_64
sclo-php72-php-pecl-imagick-3.4.4-3.el7.x86_64
ImageMagick-6.9.10.68-3.el7.x86_64