an Error has Occurred Cannot set property muted of null

I specify that this error is only in the last Appian Release, before it worked correctly

I have the same issue in the webvideo of a billboard. When I comment the webvideo code, the error goes away. All parameters of webvideo are set properly. This is a new 20.1 issue. Please help. I want to have a webvideo in my billboard. Now I am having to put an image.  Appian Community

Did this work in 19.4 and now it doesn't in 20.1? If so, I'd recommend opening a ticket with Appian support.

In JavaScript almost everything is an object, null and undefined are exception. if a variable has been declared, but has not been assigned a value, is automatically assigned the value undefined . Therefore, if you try to access the value of such variable, it will throw Uncaught TypeError cannot set property '0' of undefined/null .

JavaScript null and undefined is one of the main reasons to produce a runtime errors . This happens because you don't check the value of unknown return variables before using it. If you are not sure a variable that will always have some value, the best practice is to check the value of variables for null or undefined before using them. The standard way to catch null and undefined simultaneously is this:

if (variable == null) {
// your code here.
}

Because null == undefined is true, the above code will catch both null and undefined.

Also you can write equivalent to more explicit but less concise:

if (variable === undefined variable === null) {
// your code here.
}

This should work for any variable that is either undeclared or declared and explicitly set to null or undefined.