update changelog

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 * In `vars` array, correctly indicate whether `module` variables are `mutated` or `reassigned` ([#3215](https://github.com/sveltejs/svelte/issues/3215))
 * Fix spread props not updating in certain situations ([#3521](https://github.com/sveltejs/svelte/issues/3521), [#4480](https://github.com/sveltejs/svelte/issues/4480))
+* Use the fallback content for slots if they are passed only whitespace ([#4092](https://github.com/sveltejs/svelte/issues/4092))
 * In `dev` mode, check for unknown props even if the component has no writable props ([#4323](https://github.com/sveltejs/svelte/issues/4323))
 * Exclude global variables from `$capture_state` ([#4463](https://github.com/sveltejs/svelte/issues/4463))
 * Fix bitmask overflow for slots ([#4481](https://github.com/sveltejs/svelte/issues/4481))