[API] Inconsistent error message when deleting a tag

Fehler
1

When trying to delete a non-existent topic with the API, I get this (somewhat) understandable error:

status=403
content={"errors":["You are not permitted to view the requested resource."], 
    "error_type":"invalid_access"}

When trying to delete a non-existent tag, I get this:

status=500 
content=NoMethodError in TagsController#destroy - 
    undefined method `destroy' for nil:NilClass
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2

API can be better here, pr-welcome for that.

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3

I’ll take a stab at fixing this.

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4

Link to my fix: https://github.com/discourse/discourse/pull/5213

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5

^ PR has been merged on Oct 2 :allthethings:

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