msi: Clear the cert pointer in MsiGetFileSignatureInformation.

dlls/msi/msi.c

@@ -2580,6 +2580,7 @@ HRESULT WINAPI MsiGetFileSignatureInformationW( LPCWSTR path, DWORD flags, PCCER
     data.dwProvFlags         = 0;
     data.dwUIContext         = WTD_UICONTEXT_INSTALL;
     hr = WinVerifyTrustEx( INVALID_HANDLE_VALUE, &generic_verify_v2, &data );
+    *cert = NULL;
     if (FAILED(hr)) goto done;
 
     if (!(signer = WTHelperGetProvSignerFromChain( data.hWVTStateData, 0, FALSE, 0 )))

dlls/msi/tests/msi.c

@@ -11794,8 +11794,10 @@ static void test_MsiGetFileSignatureInformation(void)
     hr = MsiGetFileSignatureInformationA( "signature.bin", 0, NULL, NULL, &len );
     ok(hr == E_INVALIDARG, "expected E_INVALIDARG got 0x%08x\n", hr);
 
+    cert = (const CERT_CONTEXT *)0xdeadbeef;
     hr = MsiGetFileSignatureInformationA( "signature.bin", 0, &cert, NULL, &len );
     todo_wine ok(hr == HRESULT_FROM_WIN32(ERROR_FUNCTION_FAILED), "got 0x%08x\n", hr);
+    ok(cert == NULL, "got %p\n", cert);
 
     DeleteFileA( "signature.bin" );
 }