Safari won't force quit
In MacOS 10.13.1 Safari on my Macbook Pro (mid 2012) has begun to freeze and won't force quit. The icon in the dock says "Application not responding" but clicking Force Quit does nothing. In the Force Quit Applications window it DOES NOT say "not responding" but likewise does not quit using the Force Quit button. The only way to quit it is to force a reboot by holding down the power key (since it won't reboot without Safari quitting). Please help.
MacBook Pro (15-inch Mid 2012), OS X El Capitan (10.11.1)