#vulnerable code 
                                public static void parse(final PgDatabase database, final String command) {
        final Parser parser = new Parser(command);
        parser.expect("ALTER", "TABLE");
        parser.expectOptional("ONLY");

        final String tableName = parser.parseIdentifier();

        final PgTable table = database.getSchema(
                ParserUtils.getSchemaName(tableName, database)).getTable(
                ParserUtils.getObjectName(tableName));

        while (!parser.expectOptional(";")) {
            if (parser.expectOptional("ALTER")) {
                parseAlterColumn(parser, table);
            } else if (parser.expectOptional("CLUSTER", "ON")) {
                table.setClusterIndexName(parser.parseIdentifier());
            } else if (parser.expectOptional("OWNER", "TO")) {
                // we do not parse this one so we just consume the expression
                parser.getExpression();
            } else if (parser.expectOptional("ADD")) {
                if (parser.expectOptional("FOREIGN", "KEY")) {
                    parseAddForeignKey(parser, table);
                } else if (parser.expectOptional("CONSTRAINT")) {
                    parseAddConstraint(parser, table);
                } else {
                    parser.throwUnsupportedCommand();
                }
            } else if (parser.expectOptional("ENABLE")) {
                parseEnable(parser);
            } else if (parser.expectOptional("DISABLE")) {
                parseDisable(parser);
            } else {
                parser.throwUnsupportedCommand();
            }

            if (parser.expectOptional(";")) {
                break;
            } else {
                parser.expect(",");
            }
        }
    } 
                            #location 9 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                public static void parse(final PgDatabase database, final String command) {
        final Parser parser = new Parser(command);
        parser.expect("ALTER", "TABLE");
        parser.expectOptional("ONLY");

        final String tableName = parser.parseIdentifier();
        final String schemaName =
                ParserUtils.getSchemaName(tableName, database);
        final PgSchema schema = database.getSchema(schemaName);
        final String objectName = ParserUtils.getObjectName(tableName);

        final PgTable table = schema.getTable(objectName);

        if (table == null) {
            final PgView view = schema.getView(objectName);

            if (view != null) {
                parseView(parser, view);
                return;
            }
        }

        while (!parser.expectOptional(";")) {
            if (parser.expectOptional("ALTER")) {
                parseAlterColumn(parser, table);
            } else if (parser.expectOptional("CLUSTER", "ON")) {
                table.setClusterIndexName(parser.parseIdentifier());
            } else if (parser.expectOptional("OWNER", "TO")) {
                // we do not parse this one so we just consume the expression
                parser.getExpression();
            } else if (parser.expectOptional("ADD")) {
                if (parser.expectOptional("FOREIGN", "KEY")) {
                    parseAddForeignKey(parser, table);
                } else if (parser.expectOptional("CONSTRAINT")) {
                    parseAddConstraint(parser, table);
                } else {
                    parser.throwUnsupportedCommand();
                }
            } else if (parser.expectOptional("ENABLE")) {
                parseEnable(parser);
            } else if (parser.expectOptional("DISABLE")) {
                parseDisable(parser);
            } else {
                parser.throwUnsupportedCommand();
            }

            if (parser.expectOptional(";")) {
                break;
            } else {
                parser.expect(",");
            }
        }
    }