ntdll: Ignore the preload start address if it is zero.

Signed-off-by: Alexandre Julliard <julliard@winehq.org>

dlls/ntdll/virtual.c

@@ -1597,6 +1597,7 @@ void virtual_init(void)
             preload_reserve_start = (void *)start;
             preload_reserve_end = (void *)end;
             /* some apps start inside the DOS area */
+            if (preload_reserve_start)
                 address_space_start = min( address_space_start, preload_reserve_start );
         }
     }