[TIMOB-18243] Allow clearing defaut header

iphone/Classes/TiNetworkHTTPClientProxy.m

@@ -1,6 +1,6 @@
 /**
  * Appcelerator Titanium Mobile
- * Copyright (c) 2009-2014 by Appcelerator, Inc. All Rights Reserved.
+ * Copyright (c) 2009-2015 by Appcelerator, Inc. All Rights Reserved.
  * Licensed under the terms of the Apache Public License
  * Please see the LICENSE included with this distribution for details.
  */
@@ -83,6 +83,13 @@ -(void)open:(id)args
     [httpRequest setMethod: method];
     [httpRequest setUrl:url];
 
+    // twitter specifically disallows X-Requested-With so we only add this normal
+    // XHR header if not going to twitter. however, other services generally expect
+    // this header to indicate an XHR request (such as RoR)
+    if ([[url absoluteString] rangeOfString:@"twitter.com"].location==NSNotFound)
+    {
+        [httpRequest addRequestHeader:@"X-Requested-With" value:@"XMLHttpRequest"];
+    }
     if ( (apsConnectionManager != nil) && ([apsConnectionManager willHandleURL:url]) ){
         apsConnectionDelegate = [[apsConnectionManager connectionDelegateForUrl:url] retain];
     }
@@ -141,13 +148,6 @@ -(void)send:(id)args
     if([self valueForUndefinedKey:@"domain"]) {
         // TODO: NTLM
     }
-    // twitter specifically disallows X-Requested-With so we only add this normal
-    // XHR header if not going to twitter. however, other services generally expect
-    // this header to indicate an XHR request (such as RoR)
-    if ([[self valueForUndefinedKey:@"url"] rangeOfString:@"twitter.com"].location==NSNotFound)
-    {
-        [httpRequest addRequestHeader:@"X-Requested-With" value:@"XMLHttpRequest"];
-    }
     id file = [self valueForUndefinedKey:@"file"];
     if(file) {
         NSString *filePath = nil;
@@ -415,7 +415,10 @@ -(void)setOnredirect:(id)callback
 -(void)setRequestHeader:(id)args
 {
     ENSURE_ARG_COUNT(args,2);
-    [self ensureClient];
+    if (httpRequest == nil) {
+        NSLog(@"[ERROR] No request object found. Did you call open?");
+        return;
+    }
     NSString *key = [TiUtils stringValue:[args objectAtIndex:0]];
     NSString *value = [TiUtils stringValue:[args objectAtIndex:1]];
     [httpRequest addRequestHeader:key value:value];