Merge pull request #13295 from aimxhaisse/13294-mflag-panic

Fix panic when using default-initialized FlagSet
Upstream-commit: fc4f3e5650493faed1e89bcf9a2a1a61c13dcd34
Component: engine

components/engine/pkg/mflag/flag.go

@@ -560,7 +560,7 @@ func defaultUsage(f *FlagSet) {
 // Usage prints to standard error a usage message documenting all defined command-line flags.
 // The function is a variable that may be changed to point to a custom function.
 var Usage = func() {
-	fmt.Fprintf(CommandLine.output, "Usage of %s:\n", os.Args[0])
+	fmt.Fprintf(CommandLine.Out(), "Usage of %s:\n", os.Args[0])
 	PrintDefaults()
 }