VERY FAST AND SIMPLE SOLUTION:
I have reported it also as a bug and I found a very fast and quick solution:
Delete the kernel from boot that doesnt correspond to your device, for example if you have a rpi3b delete the kernel.img and if you have other rpi delete the kernel7.img and you will have space.
You need to go to /boot and do it as admin:
rm kernel.img or kernel7.img depending on the device.