Avoid highlighting the plus/minus sign

When there are no whitespaces and the first character is highlighted, the plus sign (or minus) is also highlighted.
It should remain as it was (white):

<img width="170" alt="Image" src="https://github.com/user-attachments/assets/e14999ea-3b2b-47cc-a0b1-7ba7a0a1c78b" />