Add further exception handle for relative path conversion,

accounting for paths which are not deemed 'absolute' (apparently NUL file on Windows satisfies this) #517

src/serena/project.py

@@ -192,7 +192,11 @@ class Project:
                     abs_file_path = os.path.join(root, file)
                     try:
                         if not self.is_ignored_path(abs_file_path):
-                            rel_file_path = os.path.relpath(abs_file_path, start=self.project_root)
+                            try:
+                                rel_file_path = os.path.relpath(abs_file_path, start=self.project_root)
+                            except Exception as e:
+                                log.warning("Ignoring path '%s' because it appears to be outside of the project root (%s)", abs_file_path, self.project_root)
+                                continue
                             rel_file_paths.append(rel_file_path)
                     except FileNotFoundError:
                         log.warning(