fixed schema selector

Author: Chris Car

dist/aframe-ui-modal-component.js

@@ -56,7 +56,7 @@
 
 	    schema: {
 	        src: {
-	            type: selector,
+	            type: 'selector',
 	            default: ''
 	        },
 	        show: {

dist/aframe-ui-modal-component.min.js

@@ -10,7 +10,7 @@ AFRAME.registerComponent('ui-modal', {
 
     schema: {
         src: {
-            type: selector,
+            type: 'selector',
             default: ''
         },
         show: {