Importing from OTRS 6: Error 500 "undefined method 'each' for nil:NilClass?"

[Olray]

Infos:

• Used Zammad version: 5.0.x
• Used Zammad installation type: package
• Operating system: Linux Mint based on Ubuntu
• Browser + version: Mozilla Firefox 97.0.1 (x64)

Expected behavior:

• Zammad 5.0.x starts importing tickets from OTRS

Actual behavior:

• Display of “Status Code 500: Error ID ZZlsCWVz: Please contact your adninistrator.”

Steps to reproduce the behavior:

• Start browser, surf to Zammad start page, click on “Migration from another system”, chose OTRS, enter URL given from OTRS-Addon, click “Migrate OTRS data”.

Logfile excerpt:

#/var/log/zamad/production.log

I, [2022-02-27T16:14:55.352262 #19483-174300] INFO – : Started POST “/api/v1/import/otrs/url_check” for 127.0.0.1 at 2022-02-27 16:14:55 +0100
I, [2022-02-27T16:14:55.355178 #19483-174300] INFO – : Processing by ImportOtrsController#url_check as JSON
I, [2022-02-27T16:14:55.355225 #19483-174300] INFO – : Parameters: {“url”=>“http://otrs.hostingundservice.de/otrs/public.pl?Action=ZammadMigrator;Key=”}
I, [2022-02-27T16:14:55.767512 #19483-174300] INFO – : Setting.set(‘import_backend’, “otrs”)
I, [2022-02-27T16:14:55.770151 #19483-174300] INFO – : Setting.set(‘import_otrs_endpoint’, “http://otrs.hostingundservice.de/otrs/public.pl?Action=ZammadMigrator”)
I, [2022-02-27T16:14:55.772812 #19483-174300] INFO – : Setting.set(‘import_otrs_endpoint_key’, “”)
I, [2022-02-27T16:14:55.774521 #19483-174300] INFO – : Completed 200 OK in 419ms (Views: 0.1ms | ActiveRecord: 1.7ms | Allocations: 9914)
I, [2022-02-27T16:14:58.981778 #19483-174360] INFO – : Started POST “/api/v1/import/otrs/import_check” for 127.0.0.1 at 2022-02-27 16:14:58 +0100
I, [2022-02-27T16:14:58.984550 #19483-174360] INFO – : Processing by ImportOtrsController#import_check as JSON
I, [2022-02-27T16:14:58.988036 #19483-174360] INFO – : thread#-: POST: http://otrs.hostingundservice.de/otrs/public.pl?Action=ZammadMigrator
I, [2022-02-27T16:14:58.988069 #19483-174360] INFO – : thread#-: PARAMS: {:Subaction=>“List”, :Action=>“ZammadMigrator”, :Key=>“”}
I, [2022-02-27T16:14:59.436988 #19483-174360] INFO – : thread#-: POST: http://otrs.hostingundservice.de/otrs/public.pl?Action=ZammadMigrator
I, [2022-02-27T16:14:59.437064 #19483-174360] INFO – : thread#-: PARAMS: {:Subaction=>“Export”, :Object=>“DynamicField”, :Limit=>“”, :Offset=>“”, :Diff=>0, :Action=>“ZammadMigrator”, :Key=>“”}
E, [2022-02-27T16:14:59.897351 #19483-174360] ERROR – : undefined method each' for nil:NilClass (NoMethodError) app/controllers/import_otrs_controller.rb:132:in import_check’
app/controllers/application_controller/has_download.rb:21:in block (4 levels) in <module:HasDownload>' app/controllers/application_controller/has_download.rb:20:in block (3 levels) in module:HasDownload’
app/controllers/application_controller/has_download.rb:19:in block (2 levels) in <module:HasDownload>' app/controllers/application_controller/handles_transitions.rb:16:in handle_transaction’
E, [2022-02-27T16:14:59.899098 #19483-174360] ERROR – : Error ID F3HWE5S9: undefined method `each’ for nil:NilClass
I, [2022-02-27T16:14:59.899283 #19483-174360] INFO – : Completed 500 Internal Server Error in 915ms (Views: 0.1ms | ActiveRecord: 0.5ms | Allocations: 7036)

[Olray]

Additional info:

ruby --version

ruby 2.7.4p191 (2021-07-07 revision a21a3b7d23) [x86_64-linux]

Installed Addons in OTRS 6.0:

Znuny4OTRS-Repo-6.0.76.opm
Znuny4OTRS-ZammadMigrator-6.0.7.opm