Cannot read property 'states' of undefined

[Dilergore]

Hello,

• My Home Assistant version: 2021.8.8
• My lovelace configuration method: yaml
• What I am doing: Seeing issues with the configured card
• What I expected to happen: No issues :)
• What happened instead: Getting "Uncaught (in promise) TypeError: Cannot read property 'states' of undefined"

Minimal steps to reproduce:

          - type: custom:vertical-stack-in-card
            title: Lights
            cards:
              - type: custom:slider-entity-row
                entity: light.standinglamp_office
                icon: mdi:floor-lamp
                name: "Standing Lamp"
                toggle: true
                min: 1
                hide_when_off: true
            style: | 
              ha-card.type-custom-vertical-stack-in-card {
                padding: 16px;
              }

Error messages from the browser console:

Uncaught (in promise) TypeError: Cannot read property 'states' of undefined
    at nt.set hass [as hass] (slider-entity-row.js:1)
    at HTMLElement.render (slider-entity-row.js:7)
    at HTMLElement.update (slider-entity-row.js:1)
    at HTMLElement.performUpdate (slider-entity-row.js:1)
    at HTMLElement._enqueueUpdate (slider-entity-row.js:1)

---

The entity is existing and it is light group. When the page loads it takes 1-2 seconds to the rows to display, then they work fine.

[Dilergore]

I started to see another issue as well:

slider-entity-row.js:7 Uncaught (in promise) TypeError: Cannot read properties of null (reading 'clientWidth') at HTMLElement.resized (slider-entity-row.js:7) at async HTMLElement.firstUpdated (slider-entity-row.js:7)

[thomasloven]

The readme says

Add this to an entities card:

All other usage is unsupported.