Ajax: Support usage without jQuery.event

Fixes #15118
Closes gh-1588

src/ajax.js

@@ -536,7 +536,8 @@ jQuery.extend({
 		}
 
 		// We can fire global events as of now if asked to
-		fireGlobals = s.global;
+		// Don't fire events if jQuery.event is undefined in an AMD-usage scenario (#15118)
+		fireGlobals = jQuery.event && s.global;
 
 		// Watch for a new set of requests
 		if ( fireGlobals && jQuery.active++ === 0 ) {

test/unit/ajax.js

@@ -420,6 +420,22 @@ module( "ajax", {
 		};
 	});
 
+	ajaxTest( "#15118 - jQuery.ajax() - function without jQuery.event", 1, function() {
+		var holder;
+		return {
+			url: url( "data/json.php" ),
+			setup: function() {
+				holder = jQuery.event;
+				delete jQuery.event;
+			},
+			complete: function() {
+				ok( true, "Call can be made without jQuery.event" );
+				jQuery.event = holder;
+			},
+			success: true
+		};
+	});
+
 	ajaxTest( "jQuery.ajax() - context modification", 1, {
 		url: url("data/name.html"),
 		context: {},