There isn't a Utopic build. Several suggestions:
1. Hope someone with control over the build system sees this post and fixes it
2. Pop over to #hts on Freenode and ask there
3. Edit your entries in /etc/apt/sources.list or /etc/apt/sources.list.d and point to the trusty builds instead
4. Download the trusty deb from the repo:
http://apt.tvheadend.org/unstable/pool/main/t/tvheadend/
5. Build a .deb yourself from source and use dpkg to install it
Take your pick - (3) and (4) should work, (5) definitely will, while (1) and (2) will get you the best but perhaps the slowest result.