Issue Summary

You can't set "-1" to the custom field "Text Field (single line)" and it will clear the value.
The same issue happens when setting the field value in the custom field "Text Field (multi-line)" with "-1"(without line break).

jira-customfiled-minus_one.mp4

Steps to Reproduce

Step 1: Configure the custom field with "Text Field (single line)"
Step 2: Set "-1" to the field value.
Step 3: The field value will be cleared, and the value isn't "-1".

Expected Results

You can set "-1" to the custom field("Text Field (single line)")

Actual Results

You can't set "-1" to the custom field("Text Field (single line)"), and the field value is cleared.

Workaround

Use different custom field type "Number Field" instead of "Text Field (single line)" or "Text Field (multi-line)".