Fix #8482, offsetParent should not return null. Closes gh-847.

src/offset.js

@@ -138,7 +138,7 @@ jQuery.fn.extend({
 			while ( offsetParent && (!rroot.test(offsetParent.nodeName) && jQuery.css(offsetParent, "position") === "static") ) {
 				offsetParent = offsetParent.offsetParent;
 			}
-			return offsetParent;
+			return offsetParent || document.body;
 		});
 	}
 });

test/index.html

@@ -305,6 +305,9 @@ Z</textarea>
 
 		<div id="fx-tests"></div>
 	</div>
+	<map name="imgmap" id="imgmap">
+		<area shape="rect" coords="0,0,200,50">
+	</map>
 
 </body>
 </html>

test/unit/offset.js

@@ -440,7 +440,7 @@ test("chaining", function() {
 });
 
 test("offsetParent", function(){
-	expect(11);
+	expect(12);
 
 	var body = jQuery("body").offsetParent();
 	equal( body.length, 1, "Only one offsetParent found." );
@@ -464,6 +464,9 @@ test("offsetParent", function(){
 	equal( div.length, 2, "Two offsetParent found." );
 	equal( div[0], document.body, "The body is the offsetParent." );
 	equal( div[1], jQuery("#nothiddendiv")[0], "The div is the offsetParent." );
+
+	var area = jQuery("#imgmap area").offsetParent();
+	equal( area[0], document.body, "The body is the offsetParent." );
 });
 
 test("fractions (see #7730 and #7885)", function() {