fixes #1328 - setReadonly method should only blur if the currenct a…

…ctive element is that specific Tagify instance. This might not work if an external button was used to trigger this method.

src/tagify.js

@@ -1008,7 +1008,7 @@ Tagify.prototype = {
     setReadonly( toggle, attrribute ){
         var _s = this.settings
 
-        document.activeElement.blur() // exit possible edit-mode
+        this.DOM.scope.contains(document.activeElement) && document.activeElement.blur() // exit possible edit-mode
         _s[attrribute || 'readonly'] = toggle
         this.DOM.scope[(toggle ? 'set' : 'remove') + 'Attribute'](attrribute || 'readonly', true)