Error in .on('rulesChanged.queryBuilder') function when calling getRules

Plugin initializes normally, and can load previously saved rules at initialization without problem.

I've added an auto-save feature using the "rulesChanged.queryBuilder API Event as follows:

$('#queryBuilder').on('rulesChanged.queryBuilder', function(evt) {
        const blockRules = $('#queryBuilder').queryBuilder('getRules')
        console.log('Rule Changed!', blockRules)
        if (blockRules) {
            //Save the rule
            //saveRules function here
        }
    })

The problem arises if I try to clear or change the ruleset on an already initialized queryBuilder:

$('#queryBuilder').queryBuilder('clear')

or

$('#queryBuilder').queryBuilder('setRules', rules, true)

Either of the calls above will trigger the rulesChanged event, resulting in the getRules method crashing with the error:

/node_modules/jQuery-QueryBuilder/dist/js/query-builder.js:1697 Uncaught TypeError: Cannot read property 'each' of null at parse (/node_modules/jQuery-QueryBuilder/dist/js/query-builder.js:1697) at QueryBuilder.validate (/node_modules/jQuery-QueryBuilder/dist/js/query-builder.js:1749) at QueryBuilder.getRules (/node_modules/jQuery-QueryBuilder/dist/js/query-builder.js:1779)

I can probably work around it by adding an ugly try/catch or using beforeClear to destroy the listener and rebuild it again, but there really should be an integrated solution.

Start with the rulesChanged.queryBuilder handler and trace the getRules call through dist/js/query-builder.js at parse, validate, and getRules, using the reported error at line 1697 as the entry point. Reproduce the issue with clear and setRules(..., true) after initialization; done means those operations can trigger rulesChanged without getRules crashing.