taglib: fix potential null dereference.

modules/meta_engine/taglib.cpp

@@ -385,7 +385,11 @@ static void ReadMetaFromId3v2( ID3v2::Tag* tag, demux_meta_t* p_demux_meta, vlc_
 
         p_attachment = vlc_input_attachment_New( psz_name, psz_mime,
                                 psz_description, p_data, i_data );
-        if( p_attachment )
+        if( !p_attachment )
+        {
+            free( psz_description );
+            continue;
+        }
         TAB_APPEND_CAST( (input_attachment_t**),
                          p_demux_meta->i_attachments, p_demux_meta->attachments,
                          p_attachment );