Don't desallocate non allocated memory

Modified: trunk/reactos/drivers/dd/serial/circularbuffer.c

--- trunk/reactos/drivers/dd/serial/circularbuffer.c	2005-05-05 15:39:27 UTC (rev 15003)
+++ trunk/reactos/drivers/dd/serial/circularbuffer.c	2005-05-05 15:39:36 UTC (rev 15004)
@@ -32,7 +32,8 @@

 {
 	DPRINT("Serial: FreeCircularBuffer(pBuffer %p)\n", pBuffer);
 	ASSERT(pBuffer);

-	ExFreePoolWithTag(pBuffer->Buffer, SERIAL_TAG);

+	if (pBuffer->Buffer != NULL)
+		ExFreePoolWithTag(pBuffer->Buffer, SERIAL_TAG);

 	return STATUS_SUCCESS;
 }