Fix simplepie#116. mb_convert_encoding, if dealing with an unknown "f…

…rom encoding", emits an E_WARNING and proceeds to convert from ISO-8859-1, which is whacky as hell.

simplepie.inc

@@ -9439,8 +9439,8 @@ class SimplePie_Misc
 		{
 			return SimplePie_Misc::windows_1252_to_utf8($data);
 		}
-		// This is second, as behaviour of this varies only with PHP version
-		elseif (function_exists('mb_convert_encoding') && ($return = @mb_convert_encoding($data, $output, $input)))
+		// This is second, as behaviour of this varies only with PHP version (the middle part of this expression checks the encoding is supported).
+		elseif (function_exists('mb_convert_encoding') && @mb_convert_encoding("\x80", 'UTF-16BE', $input) !== "\x00\x80" && ($return = @mb_convert_encoding($data, $output, $input)))
 		{
 			return $return;
 		}