CreatePageAndSpaceIT.createSpaceAndPage is flickering

The executed javascript expression [return typeof XWiki !== 'undefined' && XWiki.actionButtons != undefined && XWiki.actionButtons.EditActions != undefined && XWiki.actionButtons.AjaxSaveAndContinue != undefined] called with the arguments [[]] does not return a boolean value [null]

java.lang.IllegalArgumentException: The executed javascript expression [return typeof XWiki !== 'undefined' && XWiki.actionButtons != undefined && XWiki.actionButtons.EditActions != undefined && XWiki.actionButtons.AjaxSaveAndContinue != undefined] called with the arguments [[]] does not return a boolean value [null]
	at org.xwiki.test.ui.XWikiWebDriver.lambda$waitUntilJavascriptCondition$8(XWikiWebDriver.java:606)
	at org.openqa.selenium.support.ui.FluentWait.until(FluentWait.java:249)
	at org.xwiki.test.ui.XWikiWebDriver.waitUntilCondition(XWikiWebDriver.java:227)
	at org.xwiki.test.ui.XWikiWebDriver.waitUntilJavascriptCondition(XWikiWebDriver.java:598)
	at org.xwiki.test.ui.po.editor.EditPage.waitUntilPageJSIsLoaded(EditPage.java:292)
	at org.xwiki.test.ui.po.BasePage.<init>(BasePage.java:120)
	at org.xwiki.test.ui.po.editor.EditPage.<init>(EditPage.java:47)
	at org.xwiki.test.ui.po.CreatePagePage.createPage(CreatePagePage.java:120)
	at org.xwiki.test.ui.po.CreatePagePage.createPage(CreatePagePage.java:110)
	at org.xwiki.test.ui.po.CreatePagePage.createPage(CreatePagePage.java:105)
	at org.xwiki.flamingo.test.docker.CreatePageAndSpaceIT.createSpaceAndPage(CreatePageAndSpaceIT.java:72)