libafl_qemu: access() size can be zero. (#3038)

Co-authored-by: Dongjia "toka" Zhang <[email protected]>

Author: forky2

libafl_qemu/src/modules/usermode/snapshot.rs

@@ -270,7 +270,7 @@ impl SnapshotModule {
 
     pub fn access(&mut self, addr: GuestAddr, size: usize) {
         // ASSUMPTION: the access can only cross 2 pages
-        debug_assert!(size > 0 && size <= SNAPSHOT_PAGE_SIZE);
+        debug_assert!(size <= SNAPSHOT_PAGE_SIZE);
         let page = addr & SNAPSHOT_PAGE_MASK;
         self.page_access(page);
         let second_page = (addr + size as GuestAddr - 1) & SNAPSHOT_PAGE_MASK;