fix: cmd `proto add` nil pointer (#2670)

cmd/kratos/internal/proto/add/add.go

@@ -20,7 +20,10 @@ var CmdAdd = &cobra.Command{
 }
 
 func run(cmd *cobra.Command, args []string) {
-	// kratos proto add helloworld/v1/helloworld.proto
+	if len(args) == 0 {
+		fmt.Println("Please enter the proto file or directory")
+		return
+	}
 	input := args[0]
 	n := strings.LastIndex(input, "/")
 	if n == -1 {