FLUID-6410: Queuing a zero-element sequence causes "hybrid time" algorithm to leave workflow incomplete

Description

This was found in the original attempt to fix FLUID-6408 via "hybrid time" - the Captions Enactor goes through a somewhat dodgy initialisation sequence in https://github.com/amb26/infusion/blob/FLUID-6148/src/framework/preferences/js/CaptionsEnactor.js#L83 which currently reads

fluid.prefs.enactor.captions.initPlayers = function (that, getYtApi, videos) {
        var promise = fluid.promise();
        var ytAPINotice = getYtApi();

        promise.then(function () {
            $(videos).each(function (index, elm) {
                that.events.onVideoElementLocated.fire($(elm));
            });
        });

        fluid.promise.follow(ytAPINotice, promise);
        return promise;
    };

This fires itself in an onCreate listener and then issues a onVideoElementLocated which then schedules the construction of a createOnEvent youTubePlayer component:

fluid.defaults("fluid.prefs.enactor.captions", {
        gradeNames: ["fluid.prefs.enactor", "fluid.viewComponent"],
        dynamicComponents: {
            player: {
                type: "fluid.prefs.enactor.captions.youTubePlayer",
                createOnEvent: "onVideoElementLocated",
                container: "{arguments}.0",
                options: {
                    model: {
                        captions: "{captions}.model.enabled"
                    }
                }
            }
        },

It seems that this is enough to kick off the bug whereby fluid.commitPotentiae attempts to reuse an already resolved sequence and the test fixture

fluid.tests.captionsTester.verifyDynamicComponentsModel = function (that, componentNames, state) {
        fluid.each(componentNames, function (name) {
            jqUnit.assertEquals("The \"" + name + "\" dynamic component model is set correctly.", state, that[name].model.captions);
        });
    };

ends up seeing the 2nd youTubePlayer as permanently partially initialised since the remainder of the workflow queue is lost.