Always pass in a blank object for arguments

This fixes an issue where preventing the default behaviour on some
events would trigger an exception. This was bacause the event relay
was expecting there to always be an object passed in for arguments,
and this wasn't always the case.

This closes https://github.com/select2/select2/issues/3431.

src/js/select2/core.js

@@ -274,7 +274,7 @@ define([
 
     this.on('query', function (params) {
       if (!self.isOpen()) {
-        self.trigger('open');
+        self.trigger('open', {});
       }
 
       this.dataAdapter.query(params, function (data) {
@@ -304,19 +304,19 @@ define([
 
           evt.preventDefault();
         } else if (key === KEYS.ENTER) {
-          self.trigger('results:select');
+          self.trigger('results:select', {});
 
           evt.preventDefault();
         } else if ((key === KEYS.SPACE && evt.ctrlKey)) {
-          self.trigger('results:toggle');
+          self.trigger('results:toggle', {});
 
           evt.preventDefault();
         } else if (key === KEYS.UP) {
-          self.trigger('results:previous');
+          self.trigger('results:previous', {});
 
           evt.preventDefault();
         } else if (key === KEYS.DOWN) {
-          self.trigger('results:next');
+          self.trigger('results:next', {});
 
           evt.preventDefault();
         }
@@ -339,9 +339,9 @@ define([
         this.close();
       }
 
-      this.trigger('disable');
+      this.trigger('disable', {});
     } else {
-      this.trigger('enable');
+      this.trigger('enable', {});
     }
   };
 
@@ -403,7 +403,7 @@ define([
       return;
     }
 
-    this.trigger('close');
+    this.trigger('close', {});
   };
 
   Select2.prototype.isOpen = function () {
@@ -421,7 +421,7 @@ define([
     }
 
     this.$container.addClass('select2-container--focus');
-    this.trigger('focus');
+    this.trigger('focus', {});
   };
 
   Select2.prototype.enable = function (args) {

src/js/select2/dropdown/closeOnSelect.js

@@ -25,7 +25,7 @@ define([
       return;
     }
 
-    this.trigger('close');
+    this.trigger('close', {});
   };
 
   return CloseOnSelect;

src/js/select2/results.js

@@ -305,7 +305,7 @@ define([
       var data = $highlighted.data('data');
 
       if ($highlighted.attr('aria-selected') == 'true') {
-        self.trigger('close');
+        self.trigger('close', {});
       } else {
         self.trigger('select', {
           data: data
@@ -427,7 +427,7 @@ define([
             data: data
           });
         } else {
-          self.trigger('close');
+          self.trigger('close', {});
         }
 
         return;

src/js/select2/selection/allowClear.js

@@ -62,7 +62,7 @@ define([
 
     this.$element.val(this.placeholder.id).trigger('change');
 
-    this.trigger('toggle');
+    this.trigger('toggle', {});
   };
 
   AllowClear.prototype._handleKeyboardClear = function (_, evt, container) {

src/js/select2/selection/clickMask.js

@@ -13,7 +13,7 @@ define([
     );
 
     this.$mask.on('mousedown touchstart click', function () {
-      self.trigger('close');
+      self.trigger('close', {});
     });
   };
 

src/js/select2/selection/search.js

@@ -184,7 +184,7 @@ define([
       data: item
     });
 
-    this.trigger('open');
+    this.trigger('open', {});
 
     this.$search.val(item.text + ' ');
   };