fix: prevent NoMethodError in mute helpers when contact is nil (#13277)

## Linear Ticket

https://linear.app/chatwoot/issue/CW-4569/nomethoderror-undefined-method-blocked-for-nil-nomethoderror

## Description
Fixes NoMethodError in ConversationMuteHelpers that occurs during
contact deletion race condition.
When a contact is deleted, there's a brief window (~50-150ms) where
contact_id becomes nil but conversations still exist. If ResolutionJob
runs during this window, the muted? method crashes trying to call
blocked? on nil.Fixes # (issue)

## Type of change

- [ ] Bug fix (non-breaking change which fixes an issue)

## How Has This Been Tested?

- Created orphaned conversations (contact_id = nil)
- Called muted?, mute!, unmute! - all return gracefully
- Verified async deletion still works correctly

## Checklist:

- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my code
- [ ] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [ ] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules



Co-authored-by: Sojan Jose <sojan@pepalo.com>

app/jobs/conversations/resolution_job.rb

@@ -16,10 +16,12 @@ class Conversations::ResolutionJob < ApplicationJob
   private
 
   def conversation_scope(account)
-    if account.auto_resolve_ignore_waiting
-      account.conversations.resolvable_not_waiting(account.auto_resolve_after)
-    else
-      account.conversations.resolvable_all(account.auto_resolve_after)
-    end
+    base_scope = if account.auto_resolve_ignore_waiting
+                   account.conversations.resolvable_not_waiting(account.auto_resolve_after)
+                 else
+                   account.conversations.resolvable_all(account.auto_resolve_after)
+                 end
+    # Exclude orphan conversations where contact was deleted but conversation cleanup is pending
+    base_scope.where.not(contact_id: nil)
   end
 end

app/models/concerns/conversation_mute_helpers.rb

@@ -2,17 +2,21 @@ module ConversationMuteHelpers
   extend ActiveSupport::Concern
 
   def mute!
+    return unless contact
+
     resolved!
     contact.update(blocked: true)
     create_muted_message
   end
 
   def unmute!
+    return unless contact
+
     contact.update(blocked: false)
     create_unmuted_message
   end
 
   def muted?
-    contact.blocked?
+    contact&.blocked? || false
   end
 end

spec/jobs/conversations/resolution_job_spec.rb

@@ -48,6 +48,21 @@ RSpec.describe Conversations::ResolutionJob do
     end
   end
 
+  # When a contact is deleted, there's a brief window (~50-150ms) where contact_id becomes nil
+  # but conversations still exist. If ResolutionJob runs during this window, muted? can crash
+  # trying to call blocked? on nil. Fixes # (issue).
+  it 'skips orphan conversations without a contact' do
+    account.update(auto_resolve_after: 14_400, auto_resolve_ignore_waiting: false) # 10 days in minutes
+    orphan_conversation = create(:conversation, account: account, last_activity_at: 13.days.ago, waiting_since: nil)
+    orphan_conversation.update_columns(contact_id: nil, contact_inbox_id: nil) # rubocop:disable Rails/SkipsModelValidations
+    resolvable_conversation = create(:conversation, account: account, last_activity_at: 13.days.ago, waiting_since: nil)
+
+    described_class.perform_now(account: account)
+
+    expect(orphan_conversation.reload.status).to eq('open')
+    expect(resolvable_conversation.reload.status).to eq('resolved')
+  end
+
   it 'adds a label after resolution' do
     account.update(auto_resolve_label: 'auto-resolved', auto_resolve_after: 14_400)
     conversation = create(:conversation, account: account, last_activity_at: 13.days.ago, waiting_since: 13.days.ago)

spec/models/conversation_spec.rb

@@ -390,6 +390,20 @@ RSpec.describe Conversation do
         .to(have_been_enqueued.at_least(:once).with(conversation, { account_id: conversation.account_id, inbox_id: conversation.inbox_id,
                                                                     message_type: :activity, content: "#{user.name} has muted the conversation" }))
     end
+
+    context 'when contact is missing' do
+      before do
+        conversation.update_columns(contact_id: nil, contact_inbox_id: nil) # rubocop:disable Rails/SkipsModelValidations
+      end
+
+      it 'does not change conversation status' do
+        expect { mute! }.not_to(change { conversation.reload.status })
+      end
+
+      it 'does not enqueue an activity message' do
+        expect { mute! }.not_to have_enqueued_job(Conversations::ActivityMessageJob)
+      end
+    end
   end
 
   describe '#unmute!' do
@@ -418,6 +432,22 @@ RSpec.describe Conversation do
         .to(have_been_enqueued.at_least(:once).with(conversation, { account_id: conversation.account_id, inbox_id: conversation.inbox_id,
                                                                     message_type: :activity, content: "#{user.name} has unmuted the conversation" }))
     end
+
+    context 'when contact is missing' do
+      let(:conversation) { create(:conversation) }
+
+      before do
+        conversation.update_columns(contact_id: nil, contact_inbox_id: nil) # rubocop:disable Rails/SkipsModelValidations
+      end
+
+      it 'does not change conversation status' do
+        expect { unmute! }.not_to(change { conversation.reload.status })
+      end
+
+      it 'does not enqueue an activity message' do
+        expect { unmute! }.not_to have_enqueued_job(Conversations::ActivityMessageJob)
+      end
+    end
   end
 
   describe '#muted?' do
@@ -433,6 +463,16 @@ RSpec.describe Conversation do
     it 'returns false if conversation is not muted' do
       expect(muted?).to be(false)
     end
+
+    context 'when contact is missing' do
+      before do
+        conversation.update_columns(contact_id: nil, contact_inbox_id: nil) # rubocop:disable Rails/SkipsModelValidations
+      end
+
+      it 'returns false' do
+        expect(muted?).to be(false)
+      end
+    end
   end
 
   describe 'unread_messages' do