Remove old try...catch for old FF

src/ajax/xhr.js

@@ -90,11 +90,6 @@ if ( xhrSupported ) {
 					callback = function( _, isAbort ) {
 						var status, statusText, responses;
 
-						// Firefox throws exceptions when accessing properties
-						// of an xhr when a network error occurred
-						// http://helpful.knobs-dials.com/index.php/Component_returned_failure_code:_0x80040111_(NS_ERROR_NOT_AVAILABLE)
-						try {
-
 						// Was never called and is aborted or complete
 						if ( callback && ( isAbort || xhr.readyState === 4 ) ) {
 							// Clean up
@@ -140,11 +135,6 @@ if ( xhrSupported ) {
 								}
 							}
 						}
-						} catch( firefoxAccessException ) {
-							if ( !isAbort ) {
-								complete( -1, firefoxAccessException );
-							}
-						}
 
 						// Call complete if needed
 						if ( responses ) {