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

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

dlls/ntdll/virtual.c

diff --git a/dlls/ntdll/virtual.c b/dlls/ntdll/virtual.c
index 7bb4eb4..1b835bc 100644
--- a/dlls/ntdll/virtual.c
+++ b/dlls/ntdll/virtual.c
@@ -1597,7 +1597,8 @@
             preload_reserve_start = (void *)start;
             preload_reserve_end = (void *)end;
             /* some apps start inside the DOS area */
-            address_space_start = min( address_space_start, preload_reserve_start );
+            if (preload_reserve_start)
+                address_space_start = min( address_space_start, preload_reserve_start );
         }
     }