Filter '!=' does not include "None" values

Summary

When using the filter '!=' to exclude issues with a certain custom field values, on top of the excluded values, issues with custom field value "none" will also be excluded.

Steps to replicate

1. Create a new project (TEST) with 4 issues
2. Create a Custom Field Select List (Single Choice) with options A, B, C
3. Assign the Custom Field values to the issues:

   Issue 1 = None
   Issue 2 = A
   Issue 3 = B
   Issue 4 = C

4. In issue navigator, apply the filter project = TEST AND "Custom Field" != B

Expected Results

Issues 1, 2, and 4 are displayed

Actual Results

Only issues 2, and 4 are displayed

Workaround

Use the filter project = TEST AND ("Custom Field" != B OR "Custom Field" is EMPTY). Then only issues with no values for the custom field are shown