HID: steam: Prevent NULL pointer dereference in steam_{recv,send}_report

In the Linux kernel, the following vulnerability has been resolved: HID: steam: Prevent NULL pointer dereference in steam_{recv,send}_report It is possible for a malicious device to forgo submitting a Feature Report. The HID Steam driver presently makes no prevision for this and de-references the 'struct hid_report' pointer obtained from the HID devices without first checking its validity. Let's change that.