Fix uncaught ApexCharts error on dashboard load (#249)

[misterbh-saashup]

Fix uncaught ApexCharts error on dashboard load

Fixes #249.

Problem

On every dashboard load, ApexCharts threw an uncaught exception while drawing the system-usage donut:

TypeError: Cannot read properties of undefined (reading 'type')
    at … apexcharts.min.js … create()

Root cause

The chart's series was built directly from /system/usage:

const series = [ result.layers_size, result.images.size, … ]

But /system/usage omits some keys depending on daemon state — on an empty daemon it returns:

{"images":{"shared_size":0,"size":0},"containers":{"size_rootfs":0},"volumes":0,"build_cache":0}

— no layers_size. So series[0] was undefined, and ApexCharts can't render an undefined data point, which is where the error originates (inside the library's create()). The chart still rendered, so it was easy to miss, but it was a real uncaught error on load.

Fix

Coerce every series value to a finite number (missing → 0) so the series is always valid:

const num = (x) => (typeof x === 'number' && isFinite(x) ? x : 0)
const series = [ num(result.layers_size), num(result.images && result.images.size), … ]

Verification

An automated 25-load check (Playwright, listening for pageerror) went from 25/25 loads erroring → 0/25, and the chart still renders (SVG present, host info populated).

Follow-up

This is the error the Playwright navigation smoke test in #248 currently tolerates. Once both this and #248 are merged, that tolerance (and the KNOWN ISSUE (#249) filter in tests/e2e/tests/01-navigation.spec.ts) can be removed.