Update CHANGELOG.md

Author: radeksimko

CHANGELOG.md

@@ -4,6 +4,10 @@ ENHANCEMENTS:
 
  - Ask for init if current folder is empty root module ([#257](https://github.com/hashicorp/terraform-ls/pull/257))
 
+BUG FIXES:
+
+ - Avoid crashing when no hover data is available for a position ([#320](https://github.com/hashicorp/terraform-ls/pull/320))
+
 INTERNAL:
 
  - Replace `sourcegraph/go-lsp` with gopls' `internal/lsp/protocol` ([#311](https://github.com/hashicorp/terraform-ls/pull/311))