fix: ensure highlighted before selecting on tab

- Ensure at least one item is highlighted before selecting on tab keypress

Closes #1030

Author: jintoppy

Diff for: src/uiSelectController.js

@@ -498,7 +498,9 @@ uis.controller('uiSelectCtrl',
         else if (ctrl.activeIndex > 0 || (ctrl.search.length === 0 && ctrl.tagging.isActivated && ctrl.activeIndex > -1)) { ctrl.activeIndex--; }
         break;
       case KEY.TAB:
-        if (!ctrl.multiple || ctrl.open) ctrl.select(ctrl.items[ctrl.activeIndex], true);
+        if ((!ctrl.multiple || ctrl.open) && ctrl.activeIndex >=0) {
+          ctrl.select(ctrl.items[ctrl.activeIndex], true); 
+        }
         break;
       case KEY.ENTER:
         if(ctrl.open && (ctrl.tagging.isActivated || ctrl.activeIndex >= 0)){