msvfw32: Fix a memory leak

[Andrew Talbot]

Changelog:
    msvfw32: Fix a memory leak.

diff --git a/dlls/msvfw32/mciwnd.c b/dlls/msvfw32/mciwnd.c
index 1e9a4f3..6d252d9 100644
--- a/dlls/msvfw32/mciwnd.c
+++ b/dlls/msvfw32/mciwnd.c
@@ -1185,6 +1185,8 @@ end_of_mci_open:
                 if (!mwi->lasterror)
                     SendDlgItemMessageW(hWnd, CTL_TRACKBAR, TBM_SETRANGEMAX, 1,
                                         SendMessageW(hWnd, MCIWNDM_GETLENGTH, 0, 0));
+
+                HeapFree(GetProcessHeap(), 0, cmdW);
             }
 
             if (wMsg == MCIWNDM_SETTIMEFORMATA)