The '>Open as markmap' command do not work for 'filename.md' files

[Fusyong]

from yesterday afternoon， and require me to select editor as this:

but all right for 'filename.mm.md' files still.

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Here is my VSCode's:

Version: 1.54.1 (user setup)
Commit: f30a9b73e8ffc278e71575118b6bf568f04587c8
Date: 2021-03-04T22:38:31.419Z
Electron: 11.3.0
Chrome: 87.0.4280.141
Node.js: 12.18.3
V8: 8.7.220.31-electron.0
OS: Windows_NT x64 10.0.17763