Fixes Wizcorp#248 - phonegap-2.4.0 terminates in IOS

With 2.4.0, NSJSONSerialization is used, thus objects returned are immutable: http://developer.apple.com/library/ios/#documentation/Foundation/Reference/NSJSONSerialization_Class/Reference/Reference.html

Any NSDictionaries from the arguments should be considered immutable.

native/ios/FacebookConnectPlugin.m

@@ -281,7 +281,7 @@ - (void) showDialog:(CDVInvokedUrlCommand*)command
     // Save the callback ID
     self.dialogCallbackId = command.callbackId;
 
-    NSMutableDictionary *options = [command.arguments lastObject];
+    NSMutableDictionary *options = [[command.arguments lastObject] mutableCopy];
     NSString* method = [[NSString alloc] initWithString:[options objectForKey:@"method"]];
     if ([options objectForKey:@"method"]) {
         [options removeObjectForKey:@"method"];