Ubuntu 18.04 install failure

[GijsVermarien]

When I try to install the package I obtain the following errors:

sudo apt-get install xenlism-wildfire-icon-theme
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following NEW packages will be installed:
  xenlism-wildfire-icon-theme
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 0 B/145 MB of archives.
After this operation, 270 MB of additional disk space will be used.
Selecting previously unselected package xenlism-wildfire-icon-theme.
(Reading database ... 139797 files and directories currently installed.)
Preparing to unpack .../xenlism-wildfire-icon-theme_2018.05_all.deb ...
Unpacking xenlism-wildfire-icon-theme (2018.05) ...
Setting up xenlism-wildfire-icon-theme (2018.05) ...
gtk-update-icon-cache: The generated cache was invalid.
WARNING: icon cache generation failed for /usr/share/icons/Xenlism-Wildfire-WednesDay

Afterwards the themes all seem to be available in Tweaks but all icons are the same for all the different days and accents.

[xenlism]

Can you use this icon them?