Cannot read properties of null (reading 'indexOf')

This error occurs when you try to call the `indexOf()` method on a null value, which is not possible.

To fix this error, you need to first check if the value is null before calling the `indexOf()` method. You can do this using an if statement, like:

if (value != null) {
   // call the indexOf() method
} else {
   // handle the null value
}

Alternatively, you can use the `?.` operator to check if the value is null before calling the `indexOf()` method. This operator is known as the Optional Chaining operator and allows you to safely access properties and methods of an object without worrying if the object is null or undefined. The code would look like:

value?.indexOf()

This will only call the `indexOf()` method if the value is not null.