As far as I understand, Photoshop was built as to cause as few errors to the operating system as possible. It looks like your hard drive only have 7GB left, assuming that you have 250GB worth of space, the recommended free space at all time is around 10-20% from the total space. That means at least you need to have 25GB free at all time. The insufficient disk space can also lead to severe disaster and crash.
Photoshop uses temporary memory (scratch disk) to build and compile your design/image into single piece of file. So it is essential for Photoshop to have that scratch disk available, or you won't be able to save your file at all. You cannot disable the warning.
The only good way is for you to free up some space by deleting old music,or bulky video files, or you can do a routine disk clean up manually.