Autocomplete Multiple model become empty string when delete digits

[ghost]

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Plunkr Case (Bug Reports)
https://stackblitz.com/edit/angular-f7xluh

Current behavior
On a multiple autocomplete, If i add some value, and start typing a new on and delete all of my digits (so the input value become an empty string), the model/form control become an empty string

Expected behavior
The model/form control should be the list of value previously selected.

Minimal reproduction of the problem with instructions
Type 'a' and select Afghanistan, type 'b' and select Bahamas, type 'c' and backspace to delete.

What is the motivation / use case for changing the behavior?
It's a problem.
I think the error is on src/app/components/autocomplete/autocomplete.ts on line 333

this code
this.onModelChange(value);

should become
if (!this.multiple) this.onModelChange(value);

otherwise the model of multiple autocomplite become empty string and lose the previous values.

• Angular version: 7.0

• PrimeNG version: ^7.0.4

• Browser: all

• Language: all

• Node (for AoT issues): 1.6.0

[kylebake]

I've been pulling my hair out with this all day. Found a workaround by modifying this line (line 161) here in primeng/components/autocomplete/autocomplete.js:

if (value.length === 0) {

becomes:

if (value.length === 0 && !this.multiple) {