When the item has a large number of options, when deselecting everything, the following error occurs in Chrome:
ERROR RangeError: Maximum call stack size exceeded
and in Firefox:
ERROR InternalError: "too much recursion"
You can reproduce this in the example (https://stackblitz.com/edit/mat-select-autocomplete-formcontrol?file=src%2Fapp%2Fapp.component.ts) by adding the following to the constructor (which simply creates many options):
for (var i=7; i<1600; i++) {
this.options.push({display: i,value: i});
}