system: handle invalid enablement in String method

Invalid enablement is only caused by bad API usage, however panicking on the spot leaves behind messy state that has to be manually cleaned up.

Signed-off-by: Ophestra Umiker <cat@ophivana.moe>

internal/system/enablement.go

@@ -24,6 +24,9 @@ var enablementString = [...]string{
 const ELen = len(enablementString)
 
 func (e Enablement) String() string {
+	if int(e) >= ELen {
+		return "<invalid enablement>"
+	}
 	return enablementString[e]
 }