doc_tree: don't error out when parsing weird yamls
doc_tree: don't error out when parsing weird yamls

thiblahute/hotdoc,hotdoc/hotdoc,hotdoc/hotdoc,thiblahute/hotdoc,thiblahute/hotdoc,hotdoc/hotdoc,thiblahute/hotdoc,hotdoc/hotdoc,hotdoc/hotdoc,thiblahute/hotdoc,hotdoc/hotdoc,thiblahute/hotdoc