lsp-dart-run error fixed #522

Job	Run time
test (ubuntu-latest, 27.2, false)	1m 9s
test (ubuntu-latest, 28.2, false)	1m 19s
test (ubuntu-latest, 29.3, false)	1m 11s
test (macos-latest, 27.2, false)	2m 14s
test (macos-latest, 28.2, false)	2m 42s
test (macos-latest, 29.3, false)	2m 40s
test (windows-latest, 27.2, false)	1m 55s
test (windows-latest, 28.2, false)	1m 57s
test (windows-latest, 29.3, false)	1m 52s
test (ubuntu-latest, snapshot, true)	49s
test (macos-latest, snapshot, true)	2m 17s
test (windows-latest, snapshot, true)	38s
	20m 43s

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