mpr: Do not omit mandatory argument to DeviceIoControl.

dlls/mpr/wnet.c

@@ -1763,6 +1763,7 @@ static DWORD get_drive_connection( WCHAR letter, LPWSTR remote, LPDWORD size )
     struct mountmgr_unix_drive *data = (struct mountmgr_unix_drive *)buffer;
     HANDLE mgr;
     DWORD ret = WN_NOT_CONNECTED;
+    DWORD bytes_returned;
 
     if ((mgr = CreateFileW( MOUNTMGR_DOS_DEVICE_NAME, GENERIC_READ|GENERIC_WRITE,
                             FILE_SHARE_READ|FILE_SHARE_WRITE, NULL, OPEN_EXISTING,
@@ -1774,7 +1775,7 @@ static DWORD get_drive_connection( WCHAR letter, LPWSTR remote, LPDWORD size )
     memset( data, 0, sizeof(*data) );
     data->letter = letter;
     if (DeviceIoControl( mgr, IOCTL_MOUNTMGR_QUERY_UNIX_DRIVE, data, sizeof(*data),
-                         data, sizeof(buffer), NULL, NULL ))
+                         data, sizeof(buffer), &bytes_returned, NULL ))
     {
         char *p, *mount_point = buffer + data->mount_point_offset;
         DWORD len;