fix(nuxt): Don't override Nuxt options if undefined (#15795)

Sometimes, the build fails because of this error: ` ERROR Cannot set
property options of #<Object> which has only a getter `

As `nuxt.options` are always defined anyway (it's also not optional in
the `Nuxt` type), we can safely delete the assertion to `{}` which
causes the error to dissapear.

Author: s1gr1d

packages/nuxt/src/vite/sourceMaps.ts

@@ -142,7 +142,6 @@ export function changeNuxtSourceMapSettings(
   nuxt: Nuxt,
   sentryModuleOptions: SentryNuxtModuleOptions,
 ): { client: UserSourceMapSetting; server: UserSourceMapSetting } {
-  nuxt.options = nuxt.options || {};
   nuxt.options.sourcemap = nuxt.options.sourcemap ?? { server: undefined, client: undefined };
 
   let previousUserSourceMapSetting: { client: UserSourceMapSetting; server: UserSourceMapSetting } = {