fix(next): Guard against missing serverSideProps

[mydea]

I don't know enough about next to be able to tell when this would happen, but as we are type-casting this above it seems prudent enough to check for existence here as well, to be on the safe side.

Fixes #7516

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	20.49 KB (+0.01% 🔺)
@sentry/browser - ES5 CDN Bundle (minified)	63.56 KB (0%)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	19.11 KB (-0.01% 🔽)
@sentry/browser - ES6 CDN Bundle (minified)	56.63 KB (0%)
@sentry/browser - Webpack (gzipped + minified)	21.68 KB (0%)
@sentry/browser - Webpack (minified)	72.17 KB (0%)
@sentry/react - Webpack (gzipped + minified)	21.72 KB (0%)
@sentry/nextjs Client - Webpack (gzipped + minified)	52.05 KB (0%)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	33.78 KB (0%)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	26.14 KB (+0.01% 🔺)
@sentry/replay ES6 CDN Bundle (gzipped + minified)	44.01 KB (+0.03% 🔺)
@sentry/replay - Webpack (gzipped + minified)	38.08 KB (+0.04% 🔺)
@sentry/browser + @sentry/tracing + @sentry/replay - ES6 CDN Bundle (gzipped + minified)	62.24 KB (+0.03% 🔺)
@sentry/browser + @sentry/replay - ES6 CDN Bundle (gzipped + minified)	55.31 KB (+0.03% 🔺)

[Lms24]

No idea either when/why this happens but the fix looks good to me. If we find out more about this we might want to adjust the type accordingly. But no need for this to happen now.

[AbhiPrasad]

As per the type, this seems like a user error (someone writing their getServerSideProps call to return undefined).

[lforst]

As per the type, this seems like a user error (someone writing their getServerSideProps call to return undefined).

My guess too! I think this fix is fine to at least make sure we don't crash.