msi/tests: Add a test for MsiGetDatabaseState() called from a custom action.

dlls/msi/tests/custom.c

@@ -56,6 +56,7 @@ static void ok_(MSIHANDLE hinst, int todo, const char *file, int line, int condi
  * or have undesired side effects should go here. */
 UINT WINAPI main_test(MSIHANDLE hinst)
 {
+    UINT res;
     IUnknown *unk = NULL;
     HRESULT hres;
 
@@ -65,6 +66,10 @@ UINT WINAPI main_test(MSIHANDLE hinst)
 
     if (unk) IUnknown_Release(unk);
 
+    /* Test MsiGetDatabaseState() */
+    res = MsiGetDatabaseState(hinst);
+    todo_wine_ok(hinst, res == MSIDBSTATE_ERROR, "expected MSIDBSTATE_ERROR, got %u\n", res);
+
     return ERROR_SUCCESS;
 }