Add null ptr to devices vec (QEMU systemmode) (#2141)

libafl_qemu/src/emu/systemmode.rs

@@ -187,6 +187,7 @@ impl DeviceSnapshotFilter {
                 for name in l {
                     v.push(name.as_bytes().as_ptr() as *mut i8);
                 }
+                v.push(core::ptr::null_mut());
                 v.as_mut_ptr()
             }
         }