fix: preserve typed value if it does not match a valid item on enter

Author: paodb

src/main/resources/META-INF/frontend/paper-chip-input-autocomplete.js

@@ -329,12 +329,14 @@ class PaperChipInputAutocomplete extends ThemableMixin(PolymerElement) {
     }
 
     _onKeyEnter() {
-				if (this.additionalItems || (this._inputValue != '' && this._inputValue != undefined)) {
-            this._saveTag(this._inputValue);
-            this.required = false;
-            this.autoValidate = false;
-            this._inputValue = '';
-				}
+			if(this._inputValue != '' && this._inputValue != undefined){
+				if(this.additionalItems || (this._filteredSource && this._filteredSource.length == 1 && this._filteredSource[0].value == this._inputValue)){
+		            this._saveTag(this._inputValue);
+		            this.required = false;
+		            this.autoValidate = false;
+		            this._inputValue = '';
+		        } 
+			}
     }
 
     _onKeyBackspace(event) {