Lock icon and "Make writable" still exist even if the file is already "Read & Write"

Steps:
1. Create Project... ->Qt Widget Project -> Mobile Qt Application, then default to finish.
2. Find *.png or *.svg file.
3. Check its property, change its property to "Read only".
4. Try to change its property by clicking "Make writable" and selecting "Make writable".
5. Check its property, it property changed to "Read & Write".

Actual Result:
The lock icon still there, and "Make writable" still can be selected.
Please refer to the attachment.