[xubuntu] The generated cache was invalid? How do I fix this?

I'm ruing Xubuntu 14.04, I'm plaing on upgrading to 16.04 next year.

Anyway, I've installed ubudao-style 1.4.5 Icon theme from the Noobslab PPA, but I'm getting a waing that ubudao-style 1.4.5 has no cache file, so I went to the Terminal as instructed and here's the results:

gtk-update-icon-cache /home/~/.icons/ubudao-style/
gtk-update-icon-cache: The generated cache was invalid.

After much digging around, I leaed that icon-theme.cache is used to avoid a lot of system call and disk seek overhead when the application starts and since the format of the cache files allows them to be memory mapped shared between multiple applications, the overall memory consumption is reduced as well.