non-exist value if

    vars:
      student:
        name: tom
        sex: male
    tasks:
    - name: task
      desc: main entry
      task:
      - func: cmd
        do:
        - name: print
          cmd: '{{.student.name}}'
        - name: print
          cmd: '{{.student.age}}'
          #          - name: print
          #            cmd: '{{.student.age | len}}'
      - func: cmd
        do:
        - name: print
          cmd: hello tom
        if: '{{eq .student.name "tom"}}'
      - func: cmd
        desc: add support if the element does not exist, then if condition should be false
          by default
        dvars:
        - name: student_age
          value: '.student.age'
        do:
        - name: assert
          desc: |
            this cmd will not evaluated as it will not reach here
            the below evaluate will cause issue, as age does not exist
            always map to a dvar first
          cmd: '{{eq .student.age "None"}}'
        - name: print
          cmd: '{{.student.age}}'
        - name: print
          cmd: |
            you will not see this message
        if: '{{eq .student_age "None"}}'
    

    loading [Config]:  ./tests/functests/upconfig.yml
    Main config:
                 Version -> 1.0.0
                  RefDir -> ./tests/functests
                 WorkDir -> cwd
              AbsWorkDir -> /up_project/up
                TaskFile -> c0122
                 Verbose -> vvv
              ModuleName -> self
               ShellType -> /bin/sh
           MaxCallLayers -> 8
                 Timeout -> 3600000
     MaxModuelCallLayers -> 256
               EntryTask -> task
      ModRepoUsernameRef -> 
      ModRepoPasswordRef -> 
    work dir: /up_project/up
    -exec task: task
    loading [Task]:  ./tests/functests/c0122
    module: [self], instance id: [dev], exec profile: []
    profile -  envVars:
    
    (*core.Cache)({
    })
    
    Task1: [task ==> task: main entry ]
    -Step1:
    self: final context exec vars:
    
    (*core.Cache)({
      "up_runtime_task_layer_number": 0,
      "student": {
        "sex": "male",
        "name": "tom"
      }
    })
    
    ~SubStep1: [print:  ]
    tom
    ~SubStep2: [print:  ]
    None
    -Step2:
    self: final context exec vars:
    
    (*core.Cache)({
      "student": {
        "name": "tom",
        "sex": "male"
      },
      "up_runtime_task_layer_number": 0
    })
    
    ~SubStep1: [print:  ]
    hello tom
    -Step3: [: add support if the element does not exist, then if condition should be false by default ]
    self: final context exec vars:
    
    (*core.Cache)({
      "student": {
        "name": "tom",
        "sex": "male"
      },
      "up_runtime_task_layer_number": 0,
      "student_age": ".student.age"
    })
    
    condition failed, skip executing step