Context operator != matching not defined dimension

[kkaarreell]

In my test I have

adjust:
  - when: swtpm != yes
    enabled: false
    because: This tests works only with SWTPM emulator

However when scheduling tests with swtpm not being defined the test is included.
To fix that I have to use

adjust:
  - when: swtpm is not defined or swtpm != yes
    enabled: false
    because: This tests works only with SWTPM emulator

but this seems unnecessary complicated and operator != (and some other operators) should have more intuitive behavior when dimension is not defined.