The refactored __get_project_conf() raises FileNotFoundError when
project.conf does not exist, whereas the original read_value()
returns None. This causes get_value() to crash for projects with
missing or incomplete project.conf files.
Catch FileNotFoundError in __get_project_conf() and return None to
restore original behavior. Remove redundant @cache from
__read_project_conf() since __get_project_conf() already provides
caching.
Assisted-by: unsloth/Qwen3.6-35B-A3B-GGUF:IQ4_NL and pi.dev
Signed-off-by: Jan Lindemann <jan@janware.com>