fix(tracing): Don't attach resource size if null

[AbhiPrasad]

Resource size can be null in some browsers, so don't set it if it's null (only set integers).

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser (incl. Tracing, Replay) - Webpack (gzipped)	65.86 KB (-0.24% 🔽)
@sentry/browser (incl. Tracing, Replay) - Webpack with treeshaking flags (gzipped)	59.46 KB (+5.8% 🔺)
@sentry/browser (incl. Tracing) - Webpack (gzipped)	31.12 KB (-0.24% 🔽)
@sentry/browser - Webpack (gzipped)	21.38 KB (-0.12% 🔽)
@sentry/browser (incl. Tracing, Replay) - ES6 CDN Bundle (gzipped)	62.72 KB (+0.12% 🔺)
@sentry/browser (incl. Tracing) - ES6 CDN Bundle (gzipped)	29.53 KB (+0.2% 🔺)
@sentry/browser - ES6 CDN Bundle (gzipped)	21.6 KB (+0.2% 🔺)
@sentry/browser (incl. Tracing, Replay) - ES6 CDN Bundle (minified & uncompressed)	197.46 KB (+0.1% 🔺)
@sentry/browser (incl. Tracing) - ES6 CDN Bundle (minified & uncompressed)	89.32 KB (+0.19% 🔺)
@sentry/browser - ES6 CDN Bundle (minified & uncompressed)	64.29 KB (+0.27% 🔺)
@sentry/browser (incl. Tracing) - ES5 CDN Bundle (gzipped)	32.22 KB (+0.29% 🔺)
@sentry/react (incl. Tracing, Replay) - Webpack (gzipped)	66.25 KB (-0.28% 🔽)
@sentry/react - Webpack (gzipped)	21.42 KB (-0.12% 🔽)
@sentry/nextjs Client (incl. Tracing, Replay) - Webpack (gzipped)	82.96 KB (-0.25% 🔽)
@sentry/nextjs Client - Webpack (gzipped)	48.21 KB (-0.22% 🔽)
@sentry-internal/feedback - Webpack (gzipped)	16.19 KB (-0.02% 🔽)

[anonrig]

Nice