Issue #1

• Go to https://en.wikipedia.org/wiki/Special:Recentchanges?tagfilter=all
• No results are displayed. This is expected, because there is no tag named "all"
• The UI shows all tags as being selected. This is wrong. None of the tags should be selected, unless the wiki has a tag named "all"

Issue #2

• Go to Special:Recentchanges and use the UI to select all available tags (this is easiest on a dev wiki or patchdemo where there are very few tags; if your wiki has no tags, use the visual editor to make an edit, use the undo feature to undo it, then wait an hour for the tag cache to expire, and the "Visual editor" and "Undo" tags should appear in the UI)
• No results are displayed. This is wrong. The updated URL includes &tagfilter=all, which is also wrong. Instead, all edits with any of the selected tags should be displayed, and the URL should include something like &tagfilter=mw-undo%7Cvisualeditor