Catchall error block fails to catch direct decendants of Exception

Because the conditional on this line checks for strictly less than instead of less than or equal to, error blocks are unable to catch any thing which is a direct descendant of Exception.

https://github.com/sinatra/sinatra/blob/eee711bce740d38a9a91aa6028688c9a6d74b23b/lib/sinatra/base.rb#L1153

Here's a quick (untested) example:

require 'sinatra'

error do
  puts "Error block called!"
end

get "/" do
  raise StandardError
end

After visiting /, the error block will not be called. If this is by design, then this seems like a strange design decision. If it isn't, then I'd be happy to open a PR for this.

Inspect the conditional in lib/sinatra/base.rb around line 1153, then reproduce the issue with the error block and GET / example from the report. Confirm that a direct descendant of Exception reaches the catchall handler and add regression coverage; done means the error block is called for that request.