Arrow transparency doesn't work correctly

[vladz99]

Describe the bug
When you reduce the transparency of the line, when you draw the arrow, the transparency changes strangely and the arrow is not uniform.

To Reproduce
Steps to reproduce the behavior:

1. Create a new file
2. Select "Line Tool"
3. Reduce the number in the "opacity" field"
4. Draw an arrow

Expected behavior
The arrow is uniform in transparency.

Screenshots

Desktop (please complete the following information):

• OS: [Windows 10]
• Version [1.6.6]

Additional context
Add any other context about the problem here.