fix(core): Skip empty integrations

[mydea]

In the case when a user adds an empty integration, we want to handle this more gracefully instead of erroring out.

Closes #7200

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	20.05 KB (+0.01% 🔺)
@sentry/browser - ES5 CDN Bundle (minified)	62.14 KB (+0.01% 🔺)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	18.68 KB (+0.02% 🔺)
@sentry/browser - ES6 CDN Bundle (minified)	55.29 KB (+0.01% 🔺)
@sentry/browser - Webpack (gzipped + minified)	20.41 KB (+0.02% 🔺)
@sentry/browser - Webpack (minified)	66.73 KB (+0.01% 🔺)
@sentry/react - Webpack (gzipped + minified)	20.44 KB (+0.02% 🔺)
@sentry/nextjs Client - Webpack (gzipped + minified)	47.78 KB (+0.01% 🔺)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	26.93 KB (+0.02% 🔺)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	25.2 KB (+0.02% 🔺)
@sentry/replay ES6 CDN Bundle (gzipped + minified)	42.52 KB (0%)
@sentry/replay - Webpack (gzipped + minified)	36.72 KB (0%)
@sentry/browser + @sentry/tracing + @sentry/replay - ES6 CDN Bundle (gzipped + minified)	60.15 KB (+0.01% 🔺)
@sentry/browser + @sentry/replay - ES6 CDN Bundle (gzipped + minified)	53.75 KB (+0.01% 🔺)