Improved url error handling.

app/assets/javascripts/app/controllers/import_zendesk.coffee

@@ -117,7 +117,7 @@ class Index extends App.ControllerContent
     e.preventDefault()
     @urlStatus.attr('data-state', '')
     url = @zendeskUrl.val() + '/agent/admin/api'
-    @zendeskUrlApiToken.attr('href', url.replace('//', '/'))
+    @zendeskUrlApiToken.attr('href', url.replace(/[^:]\/\//, '/'))
     @zendeskUrlApiToken.val('HERE')
     @$('[data-slide=zendesk-url]').toggleClass('hide')
     @$('[data-slide=zendesk-credentials]').toggleClass('hide')

app/controllers/import_zendesk_controller.rb

@@ -50,7 +50,7 @@ class ImportZendeskController < ApplicationController
     end
 
     endpoint = "#{params[:url]}/api/v2"
-    endpoint.gsub('//', '/')
+    endpoint.gsub(%r{[^:]//}, '/')
     Setting.set('import_zendesk_endpoint', endpoint)
 
     render json: {