feat(validator): add nil machine claim error

All epochs have at least one input. If an input has no outputs, then Input.OutputsHash equals the last input OutputsHash. If it is the first input and it has no outputs, its OutputsHash is the application's template hash. Therefore, if this value is nil the node is in an inconsistent state.

internal/validator/validator.go

@@ -139,8 +139,15 @@ func (v *Validator) validateApplication(ctx context.Context, app Application) er
 			)
 		}
 
+		if machineClaim == nil {
+			return fmt.Errorf(
+				"inconsistent state: machine claim for epoch %v of application %v was not found",
+				epoch.Index, epoch.AppAddress,
+			)
+		}
+
 		// ...and compare it to the hash calculated by the Validator
-		if machineClaim != nil && *machineClaim != *claim {
+		if *machineClaim != *claim {
 			return fmt.Errorf(
 				"validator claim does not match machine claim for epoch %v of application %v",
 				epoch.Index, epoch.AppAddress,