This worked perfectly for me and it's not as complicated as it seems. Even a beginner can do it. These are the steps:
1. Open Applications --> Utilities --> Terminal. Copy and paste this, then hit return to show your hidden files:
defaults write com.apple.finder AppleShowAllFiles YES
Pull down the Apple menu to Force Quit. Click on Finder, then the Relaunch button.
Your hidden files will now show.
2. Click on the desktop, then pull down the Go menu to Go To Folder.
Copy and paste this, then hit return to find your Library folder:
~/Library/
3. Open the Preferences folder inside the Library folder. Find the following items and move them to your desktop (or to a new folder on your desktop that you name "Deleted Prefs" or something that will help you find them if you need them. These are the items I moved to the desktop that solved my problem:
com.apple.commerce.safari.plist
com.apple.Safari.Extensions.plist
com.apple.Safari.LSSharedFileList.plist
com.apple.Safari.plist.lockfile
com.apple.Safari.RSS.plist
com.apple.Safari.SafeBrowsing.Service.plist
com.apple.SafariCloudHistoryPushAgent.plist
com.apple.SafariNotificationAgent.plist
com.apple.SafariPlugInUpdateNotifier.plist
com.apple.WebFoundation.plist
4. Quit Safari and reopen it. Test it thoroughly.
If you still have a problem, go back to Library --> Preferences and drag com.apple.Safari.plist to the desktop.
You will lose all your bookmarks, so don't do this unless you have to. (You can first import them to Google or Firefox if you like so you don't completely lose them.)
5. When Safari is working fine, go back to Applications --> Utilities --> Terminal, copy and paste this, then hit return:
defaults write com.apple.finder AppleShowAllFiles NO
Pull down the Apple menu to Force Quit. Click on Finder, then the Relaunch button.
Your hidden files will be hidden again now.
6. Save the Deleted Prefs for a while to make sure all is well. Then trash them.
NOTE: It's good to know how to delete preferences because often a new update will be incompatible with old preferences. It's the first thing to try when there is a problem after an update. Just find the preferences for the program that isn't working right and use these steps to delete them. They feel complicated the first time, but then become easy.