NOISSUE - Fix nil pointer dereference in Stop methods for agentServer and agentService (#409)

Signed-off-by: Sammy Oina <sammyoina@gmail.com>

agent/cvms/server/cvm.go

@@ -94,5 +94,8 @@ func (as *agentServer) Start(cfg agent.AgentConfig, cmp agent.Computation) error
 }
 
 func (as *agentServer) Stop() error {
+	if as.gs == nil {
+		return nil
+	}
 	return as.gs.Stop()
 }

agent/service.go

@@ -215,8 +215,10 @@ func (as *agentService) StopComputation(ctx context.Context) error {
 
 	as.cancel()
 
-	if err := as.algorithm.Stop(); err != nil {
-		return fmt.Errorf("error stopping computation: %v", err)
+	if as.algorithm != nil {
+		if err := as.algorithm.Stop(); err != nil {
+			return fmt.Errorf("error stopping computation: %v", err)
+		}
 	}
 
 	sm := statemachine.NewStateMachine(Idle)