fix(debug): config file handling

This commit fixes the handling of the config file in the `debug_parser` function. It now correctly checks if the config file exists before attempting to parse it. Additionally, it prints the config details for debugging purposes.

fortls/debug.py

@@ -439,7 +439,8 @@ def read_config(root: str | None):
 
         # Check for config files
         config_path = locate_config(root)
-        if not os.path.isfile(config_path):
+        print(f"  Config file = {config_path}")
+        if config_path is None or not os.path.isfile(config_path):
             return pp_suffixes, pp_defs, include_dirs
 
         try: