Fix case when _DIR variables are empty

Author: nitins17

ci/utilities/convert_msys_paths_to_win_paths.py

@@ -47,7 +47,7 @@ def main(parsed_args: argparse.Namespace):
   converted_paths = {}
 
   for var, value in os.environ.items():
-    if parsed_args.blacklist and var in parsed_args.blacklist:
+    if (parsed_args.blacklist and var in parsed_args.blacklist) or not value:
       continue
     if "_DIR" in var or (args.whitelist and var in parsed_args.whitelist):
       converted_path = msys_to_windows_path(value)