fix strict null

src/tsconfig.strictNullChecks.json

@@ -54,6 +54,7 @@
 		"./vs/editor/contrib/cursorUndo/cursorUndo.ts",
 		"./vs/editor/contrib/dnd/dnd.ts",
 		"./vs/editor/contrib/dnd/dragAndDropCommand.ts",
+		"./vs/editor/contrib/documentSymbols/outline.ts",
 		"./vs/editor/contrib/documentSymbols/outlineModel.ts",
 		"./vs/editor/contrib/find/findController.ts",
 		"./vs/editor/contrib/find/findDecorations.ts",
@@ -547,7 +548,6 @@
 		"./vs/workbench/contrib/markers/electron-browser/markersPanelActions.ts",
 		"./vs/workbench/contrib/markers/electron-browser/messages.ts",
 		"./vs/workbench/contrib/markers/test/electron-browser/markersModel.test.ts",
-		"./vs/workbench/contrib/outline/electron-browser/outline.ts",
 		"./vs/workbench/contrib/output/common/output.ts",
 		"./vs/workbench/contrib/output/common/outputLinkComputer.ts",
 		"./vs/workbench/contrib/output/common/outputLinkProvider.ts",
@@ -747,4 +747,4 @@
 	"exclude": [
 		"./typings/require-monaco.d.ts"
 	]
-}
\ No newline at end of file
+}