[Feature] disable GA if no env var set

[evereq]

See code below from apps\web\pages\_app.tsx:

<Script
				strategy="lazyOnload"
				src={`https://www.googletagmanager.com/gtag/js?id=${process.env.NEXT_PUBLIC_GA_MEASUREMENT_ID}`}
			/>
			<Script strategy="lazyOnload" id="google-analytic-script">
				{` window.dataLayer = window.dataLayer || [];
  				function gtag(){dataLayer.push(arguments);}
  				gtag('js', new Date());
  				gtag('config', '${process.env.NEXT_PUBLIC_GA_MEASUREMENT_ID}');`}
			</Script>

We need to disable loading that code if env var is NOT set (empty or undefined value)

[maceteligolden]

@evereq noted, i'll create a PR and make the changes

[maceteligolden]

@evereq here is the PR #1680