Template list type field such as watch list throws invalid email address or User error if field loses focus by clicking out or pressing TAB key

Build information:
Istanbul Patch 5

Issue Description:
When creating a new template, and adding users to a watch list if we change the focus of the pointer by clicking out of the field or TAB when adding names, the system throws a Please enter a valid email address or User error and not allow you to continue.

We have observed that there are errors thrown in the developer browser console:

isEmailValid: missing @ sign

Uncaught DOMException: Failed to execute 'removeChild' on 'Node': The node to be removed is not a child of this node.
at e.hideFieldMsg (https://istanbulpatch4.service-now.com/scripts/doctype/js_includes_doctype.jsx?v=03-22-2017_2107&lp=Wed_May_31_10_44_54_PDT_2017&c=12_252:7014:8)
at e._setFormValues (https://istanbulpatch4.service-now.com/scripts/doctype/js_includes_doctype.jsx?v=03-22-2017_2107&lp=Wed_May_31_10_44_54_PDT_2017&c=12_252:18762:8)
at e.referenceSelect (https://istanbulpatch4.service-now.com/scripts/doctype/js_includes_doctype.jsx?v=03-22-2017_2107&lp=Wed_May_31_10_44_54_PDT_2017&c=12_252:18775:6)
at e.select (https://istanbulpatch4.service-now.com/scripts/doctype/js_includes_doctype.jsx?v=03-22-2017_2107&lp=Wed_May_31_10_44_54_PDT_2017&c=12_252:18286:6)
at e.onMouseUp (https://istanbulpatch4.service-now.com/scripts/doctype/js_includes_doctype.jsx?v=03-22-2017_2107&lp=Wed_May_31_10_44_54_PDT_2017&c=12_252:18373:6)
at HTMLDivElement. (https://istanbulpatch4.service-now.com/scripts/doctype/js_includes_doctype.jsx?v=03-22-2017_2107&lp=Wed_May_31_10_44_54_PDT_2017&c=12_252:11:5254)

Screenshots attached for review

1. Create a new template for incident table
2. Select Watch List as the field and press TAB to move to the next field.
3. Type in any name then select it from the autocomplete function then press TAB again
4. Navigate back to the field, erase the first name selection, try to add a new name by typing, and then attempting to select from dropdown
   
   The system throws an error and prevents you from adding anything to watch list field.

Use the magnifying glass search functionality when adding users to a watchlist field on a template.