Fixes #8297. Makes sure response headers with empty values are handled...

Fixes #8297. Makes sure response headers with empty values are handled properly and do not prevent proper parsing of the entire response headers string. Unit test amended.

src/ajax.js

@@ -4,7 +4,7 @@ var r20 = /%20/g,
 	rbracket = /\[\]$/,
 	rCRLF = /\r?\n/g,
 	rhash = /#.*$/,
-	rheaders = /^(.*?):\s*(.*?)\r?$/mg, // IE leaves an \r character at EOL
+	rheaders = /^(.*?):[ \t]*([^\r\n]*)\r?$/mg, // IE leaves an \r character at EOL
 	rinput = /^(?:color|date|datetime|email|hidden|month|number|password|range|search|tel|text|time|url|week)$/i,
 	// #7653, #8125, #8152: local protocol detection
 	rlocalProtocol = /(?:^file|^widget|\-extension):$/,
@@ -439,7 +439,7 @@ jQuery.extend({
 						}
 						match = responseHeaders[ key.toLowerCase() ];
 					}
-					return match || null;
+					return match === undefined ? null : match;
 				},
 
 				// Overrides response content-type header

test/data/headers.php

 <?php
 
 header( "Sample-Header: Hello World" );
+header( "Empty-Header: " );
+header( "Sample-Header2: Hello World 2" );
 
 $headers = array();
 

test/unit/ajax.js

@@ -344,7 +344,7 @@ test(".ajax() - retry with jQuery.ajax( this )", function() {
 
 test(".ajax() - headers" , function() {
 
-	expect( 2 );
+	expect( 4 );
 
 	stop();
 
@@ -376,8 +376,14 @@ test(".ajax() - headers" , function() {
 			tmp.push(  "ajax-send: test\n" );
 			tmp = tmp.join( "" );
 
-			equals( data , tmp , "Headers were sent" );
-			equals( xhr.getResponseHeader( "Sample-Header" ) , "Hello World" , "Sample header received" );
+			strictEqual( data , tmp , "Headers were sent" );
+			strictEqual( xhr.getResponseHeader( "Sample-Header" ) , "Hello World" , "Sample header received" );
+			if ( jQuery.browser.mozilla ) {
+				ok( true, "Firefox doesn't support empty headers" );
+			} else {
+				strictEqual( xhr.getResponseHeader( "Empty-Header" ) , "" , "Empty header received" );
+			}
+			strictEqual( xhr.getResponseHeader( "Sample-Header2" ) , "Hello World 2" , "Second sample header received" );
 		},
 		error: function(){ ok(false, "error"); }