ole32: Avoid null pointer dereferences in CoGetTreatAsClass.

dlls/ole32/compobj.c

@@ -3825,6 +3825,10 @@ HRESULT WINAPI CoGetTreatAsClass(REFCLSID clsidOld, LPCLSID clsidNew)
     LONG len = sizeof(szClsidNew);
 
     TRACE("(%s,%p)\n", debugstr_guid(clsidOld), clsidNew);
+
+    if (!clsidOld || !clsidNew)
+        return E_INVALIDARG;
+
     *clsidNew = *clsidOld; /* copy over old value */
 
     res = COM_OpenKeyForCLSID(clsidOld, wszTreatAs, KEY_READ, &hkey);

dlls/ole32/tests/compobj.c

@@ -2176,10 +2176,18 @@ static void test_TreatAsClass(void)
         win_skip("CoGetTreatAsClass not present\n");
         return;
     }
+
     hr = pCoGetTreatAsClass(&deadbeef,&out);
     ok (hr == S_FALSE, "expected S_FALSE got %x\n",hr);
     ok (IsEqualGUID(&out,&deadbeef), "expected to get same clsid back\n");
 
+    hr = pCoGetTreatAsClass(NULL, &out);
+    ok(hr == E_INVALIDARG, "expected E_INVALIDARG got %08x\n", hr);
+    ok(IsEqualGUID(&out, &deadbeef), "expected no change to the clsid\n");
+
+    hr = pCoGetTreatAsClass(&deadbeef, NULL);
+    ok(hr == E_INVALIDARG, "expected E_INVALIDARG got %08x\n", hr);
+
     lr = RegOpenKeyExA(HKEY_CLASSES_ROOT, "CLSID", 0, KEY_READ, &clsidkey);
     ok(!lr, "Couldn't open CLSID key, error %d\n", lr);