An error occurred
Backport #21639 An error occurred . Fixed #21636 An error occurred . Related to #20987 An error occurred . A markdown template without metadata should not be treated as an invalid template. And this PR fixed another bug that non-template files(neither .md nor .yaml) are treated as yaml files. <img width="504" alt="image" src="https://user-images.githubusercontent.com/9418365/198968668-40082fa1-4f25-4d3e-9b73-1dbf6d1a7521.png">
Jason Song
