Creating an epic reference in the description field causes a 500 error when saving

Creating an epic reference in the description field causes a 500 error when saving, though the update partially succeeds.

Steps to Reproduce:

1. Create a new epic
2. Navigate to the epic's edit page
3. Add a reference to another epic in the description field (e.g., #123 (closed) or epic link)
4. Click the Save button

Expected Behavior:

• Epic description should update successfully
• System notes should be created showing the connection between the two epics
• No errors should occur

Actual Behavior:

• Network request returns a 500 error
• Error is logged in Sentry
• After page refresh, the description is updated correctly
• System notes showing the epic connection are missing

Technical Details:

• The error originates from the system notes creation class (same class referenced in Sentry error logs)
• The description update succeeds, but the system note generation fails
• This suggests the issue is specifically with the system notes creation process when processing epic references

Impact:

• User receives an error despite partial success
• Epic relationships are not properly tracked in system notes

Demo of the bug: bug_epic