[MAD Decoder] Do not close source ourselves

The input isn't supposed to close its own sources, as it did not open
them itself, and they should be cleaned up automatically when they are
released to zero reference count.

Signed-off-by: Christopher Snowhill <kode54@gmail.com>

Plugins/MAD/MADDecoder.m

@@ -780,7 +780,6 @@ error:
 
 - (void)close {
 	if(_source) {
-		[_source close];
 		_source = nil;
 	}