Gauges do not handle missing objects

[akhenry]

Summary

A missing object in a Gauge will throw a JavaScript error in the console. The issue appears to be in this line of code, which assumes at least one range is returned -

openmct/src/plugins/gauge/components/GaugeComponent.vue

Line 656 in 057a5f9

this.valueKey = this.metadata.valuesForHints(['range'])[0].source;

Expected vs Current Behavior

There should not be any unhandled errors in the JavaScript console