Prometheus fixes

[lenisko]

Possibly solve

TypeError: Value is not a valid number: undefined
    at set (/home/rotom/node_modules/prom-client/lib/gauge.js:144:9)
    at Gauge.set (/home/rotom/node_modules/prom-client/lib/gauge.js:30:3)
    at forEach (/home/rotom/dist/packages/server/webpack:/rotom/packages/server/src/index.ts:292:41)
    at Array.forEach (<anonymous>)
    at Timeout._onTimeout (/home/rotom/dist/packages/server/webpack:/rotom/packages/server/src/index.ts:288:38)
    at listOnTimeout (node:internal/timers:569:17)
    at processTimers (node:internal/timers:512:7)
TypeError: Value is not a valid number: undefined
    at set (/home/rotom/node_modules/prom-client/lib/gauge.js:144:9)
    at Gauge.set (/home/rotom/node_modules/prom-client/lib/gauge.js:30:3)
    at forEach (/home/rotom/dist/packages/server/webpack:/rotom/packages/server/src/index.ts:292:41)
    at Array.forEach (<anonymous>)
    at Timeout._onTimeout (/home/rotom/dist/packages/server/webpack:/rotom/packages/server/src/index.ts:288:38)
    at listOnTimeout (node:internal/timers:569:17)
    at processTimers (node:internal/timers:512:7) Uncaught Exception thrown
2023-11-20 22:14:51.923  ERROR TypeError: Value is not a valid number: undefined
    at set (/home/rotom/node_modules/prom-client/lib/gauge.js:144:9)
    at Gauge.set (/home/rotom/node_modules/prom-client/lib/gauge.js:30:3)
    at forEach (/home/rotom/dist/packages/server/webpack:/rotom/packages/server/src/index.ts:292:41)
    at Array.forEach (<anonymous>)
    at Timeout._onTimeout (/home/rotom/dist/packages/server/webpack:/rotom/packages/server/src/index.ts:288:38)
    at listOnTimeout (node:internal/timers:569:17)
    at processTimers (node:internal/timers:512:7) Uncaught Exception thrown 

[Fabio1988]

The null coalescing operator would have been better than the OR operator
Also, the Number.isFinite operator doesn't convert string. I'm not sure the values returned are valid Numbers