docs: update CHANGELOG

[skip ci]

Author: gnikit

CHANGELOG.md

@@ -24,6 +24,9 @@
 
 ### Fixed
 
+- Fixed bug where diagnostic messages were raised for non-existent variables
+  ([#173](https://github.com/fortran-lang/fortls/issues/173))
+  ([#175](https://github.com/fortran-lang/fortls/issues/175))
 - Fixed submodule crashing bug and document/Symbol request failure
   ([#233](https://github.com/fortran-lang/fortls/issues/233))
 - Fixed debug interface parser not loading all configuration files