Make arg display a little more paranoid, fixes #2405

Changes.md

@@ -1,3 +1,8 @@
+HEAD
+-----------
+
+- Safer display of job data in Web UI [#2405]
+
 3.4.1
 -----------
 

lib/sidekiq/web_helpers.rb

@@ -169,11 +169,22 @@ module Sidekiq
 
     def display_args(args, truncate_after_chars = 2000)
       args.map do |arg|
-        a = arg.inspect
-        h(truncate(a))
+        h(truncate(to_display(arg)))
       end.join(", ")
     end
 
+    def to_display(arg)
+      begin
+        arg.inspect
+      rescue
+        begin
+          arg.to_s
+        rescue => ex
+          "Cannot display argument: [#{ex.class.name}] #{ex.message}"
+        end
+      end
+    end
+
     RETRY_JOB_KEYS = Set.new(%w(
       queue class args retry_count retried_at failed_at
       jid error_message error_class backtrace