Map zero page, like e820 does

xtldr/amd64/memory.c

@@ -99,6 +99,9 @@ BlEnablePaging(IN PLIST_ENTRY MemoryMappings,
         ListEntry = ListEntry->Flink;
     }
 
+    /* Map zero page as well */
+    BlMapVirtualMemory(MemoryMappings, 0, 0, 1, PtePointer);
+
     /* Allocate and zero-fill buffer for EFI memory map */
     BlEfiMemoryAllocatePool(sizeof(EFI_MEMORY_MAP), (PVOID*)&MemoryMap);
     RtlZeroMemory(MemoryMap, sizeof(EFI_MEMORY_MAP));