msi: MsiDatabaseCommit also succeeds for a a readonly database.

dlls/msi/msiquery.c

@@ -831,6 +831,12 @@ UINT WINAPI MsiDatabaseCommit( MSIHANDLE hdb )
         return ERROR_SUCCESS;
     }
 
+    if (db->mode == MSIDBOPEN_READONLY)
+    {
+        msiobj_release( &db->hdr );
+        return ERROR_SUCCESS;
+    }
+
     /* FIXME: lock the database */
 
     r = MSI_CommitTables( db );

dlls/msi/tests/db.c

@@ -96,6 +96,9 @@ static void test_msidatabase(void)
     res = MsiOpenDatabase( msifile, MSIDBOPEN_READONLY, &hdb );
     ok( res == ERROR_SUCCESS , "Failed to open database\n" );
 
+    res = MsiDatabaseCommit( hdb );
+    ok( res == ERROR_SUCCESS , "Failed to commit database\n" );
+
     res = MsiCloseHandle( hdb );
     ok( res == ERROR_SUCCESS , "Failed to close database\n" );