Silence unneeded exception to allow easier ACM debugging.

dlls/msacm/internal.c

diff --git a/dlls/msacm/internal.c b/dlls/msacm/internal.c
index 2479368..e9d2bd3 100644
--- a/dlls/msacm/internal.c
+++ b/dlls/msacm/internal.c
@@ -147,7 +147,7 @@
 {
     PWINE_ACMOBJ	pao = (PWINE_ACMOBJ)hObj;
 
-    if (IsBadReadPtr(pao, sizeof(WINE_ACMOBJ)) ||
+    if (pao == NULL || IsBadReadPtr(pao, sizeof(WINE_ACMOBJ)) ||
 	((type != WINE_ACMOBJ_DONTCARE) && (type != pao->dwType)))
 	return NULL;
     return pao;