empty string values break dynamic batch connect forms

[johrstrom]

From discourse: https://discourse.openondemand.org/t/cant-seem-to-get-data-hide-working/4584

Consider this form below. When using the "None" value (actual value "") in a select widget to hide another widget, this currently breaks the javascript as we're unable to handle the edge case.

---
cluster: pitzer

attributes:
  sn_gpu:
    widget: select
    label: GPU
    display: true
    options:
      - [ "None", "", data-hide-sn-virtualgl: true ]
      - [ "h100 (80GB)", "h100:1" ]
  sn_virtualgl:
    widget: "check_box"
    label: "Enable VirtualGL (if hardware OpenGL required)"
    checked_value: "yes"
    unchecked_value: "no"
form:
  - sn_gpu
  - sn_virtualgl

[johrstrom]

I have a patch for this coming, I just need to write a test case.