[webui] do not crash when handling remote instance with invalid SSL CA

This happened when adding packman OBS instance and trying to add
a repository in the simple webui view.

Repository targets won't become visible anyway.

src/api/app/models/distribution.rb

@@ -49,7 +49,13 @@ def self.all_including_remotes
     remote_projects = Project.where("NOT ISNULL(projects.remoteurl)")
     remote_projects.each do |prj|
       body = Rails.cache.fetch("remote_distribution_#{prj.id}", expires_in: 1.hour) do
-        ActiveXML.backend.load_external_url(prj.remoteurl + "/distributions.xml")
+        begin
+          ActiveXML.backend.load_external_url(prj.remoteurl + "/distributions.xml")
+        rescue OpenSSL::SSL::SSLError
+          # skip, but do not die if remote instance have invalid SSL
+          Rails.logger.error "Remote instance #{prj.remoteurl} has no valid SSL certificate"
+          next
+        end
       end
       next if body.blank? # don't let broken remote instances break us
       xmlhash = Xmlhash.parse(body)