Minutes field doesn't render if minutes is :00

[darac]

Checklist:

• I updated to the latest version available
• I cleared the cache of my browser

The problem

When displaying a time with zero minutes (e.g. xx:00), the minutes component doesn't render.

Environment

• time-picker-card release with the issue: 1.4.0
• Last working time-picker-card release (if known):
• Browser and Operating System: Firefox 144.0 on Debian Linux 13
• Home Assistant version: 2025.10.4

Problem-relevant configuration

I am using time-picker-card as part of the Growatt integration, which embeds time-picker-card within a vertical-stack card, but the configuration of time-picker-card is:

  - type: custom:time-picker-card
    entity: input_datetime.adgw_battery_first_time_slot_2_start
    name: "2"
    hour_mode: 24
    hour_step: 1
    minute_step: 5
    layout:
      hour_mode: double
      align_controls: center
      name: inside
      embedded: false
      thin: true
    hide:
      seconds: true
      name: true
      icon: true
    link_values: false
    card_mod:
      style: |
        ha-card {
          margin: 0px;
          border: none;
          background: none;
        }

Javascript errors shown in the web inspector (if applicable):

Uncaught (in promise) TypeError: can't access property "toString", this.value is undefined
    toString time-picker-card.js:150
    render time-picker-card.js:86
    update time-picker-card.js:23
    performUpdate time-picker-card.js:11
    scheduleUpdate time-picker-card.js:11
    _$Ej time-picker-card.js:11
    requestUpdate time-picker-card.js:11
    set time-picker-card.js:11
    j time-picker-card.js:17
    _$AI time-picker-card.js:17
    p time-picker-card.js:17
    $ time-picker-card.js:17
    _$AI time-picker-card.js:17
    Do time-picker-card.js:23
    update time-picker-card.js:23
    performUpdate time-picker-card.js:11
    scheduleUpdate time-picker-card.js:11
    _$Ej time-picker-card.js:11
    requestUpdate time-picker-card.js:11
    set time-picker-card.js:11
    update hui-card.ts:213
    performUpdate reactive-element.ts:1504
    scheduleUpdate reactive-element.ts:1400
    _$EP reactive-element.ts:1372
    requestUpdate reactive-element.ts:1311
    set reactive-element.ts:789
    update hui-stack-card.ts:55
    update hui-stack-card.ts:54
    performUpdate reactive-element.ts:1504
    scheduleUpdate reactive-element.ts:1400
    _$EP reactive-element.ts:1372
    requestUpdate reactive-element.ts:1311
    set reactive-element.ts:789
    update hui-card.ts:213
    performUpdate reactive-element.ts:1504
    scheduleUpdate reactive-element.ts:1400
    _$EP reactive-element.ts:1372
    requestUpdate reactive-element.ts:1311
    set reactive-element.ts:789
    update hui-stack-card.ts:55
    update hui-stack-card.ts:54
    performUpdate reactive-element.ts:1504
    scheduleUpdate reactive-element.ts:1400
    _$EP reactive-element.ts:1372
    requestUpdate reactive-element.ts:1311
    set reactive-element.ts:789
    set hass stack-in-card.js:200
    update hui-card.ts:213
    performUpdate reactive-element.ts:1504
    scheduleUpdate reactive-element.ts:1400
    _$EP reactive-element.ts:1372
    requestUpdate reactive-element.ts:1311
    set reactive-element.ts:789
    update hui-stack-card.ts:55
    update hui-stack-card.ts:54
    performUpdate reactive-element.ts:1504
    time-picker-card.js:150:613