Problems with libgtk after upgrading to 16.04

looks like you are missing the libgtk2.0-0:amd64 package

sudo apt-get install libgtk2.0-0:amd64

I verified this by finding the file on my system and running

dpkg -S /usr/lib/x86_64-linux-gnu/libgdk-x11-2.0.so.0

my hunch is that you will have more missing libs because some part of installation didn't work right. It might be worth running these commands to ensure you have all packages you need.

sudo apt-get update
sudo apt-get dist upgrade

Edit:

it looks like you might have a corrupted version of that file you could try reinstalling that package

  sudo apt-get purge libgtk2.0-0:amd64
  sudo apt-get install libgtk2.0-0:amd64