I had this problem as well but restarting did not help. I found this fix in a GitHub issue thread that worked for me right away. Run this in the Terminal to get Safari to re-register with LaunchServices:
/System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/Support/lsregister -f /Applications/Safari.app
Source: https://github.com/ovity/octotree/issues/1110
More on lsregister (it's not currently documented in man): https://ss64.com/osx/lsregister.html
coliniloc
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I have done this at least a dozen times over the last couple of months but, for some reason, today it worked. ¯_(°-o)_/¯