Fixed bugs when grading team contributions without common project prefix

- Handles bad entry of path
- Handles project team with no students

grade_team_contribution.py

@@ -4,6 +4,8 @@ from datetime import date
 from math import ceil, log10
 from typing import Tuple
 
+from gitlab import GitlabError
+
 from api.canvas_classes import *
 from api.gitlab_classes import *
 from common_functions import select_from_list, strip_html
@@ -176,8 +178,19 @@ if __name__ == '__main__':
         print()
         if grading_git_histories:
             if no_common_prefix:
-                custom_project = input(f'Enter path to {student_group.get_name()}\'s repository: ')
-                display_git_contributions(GitlabProject(custom_project))
+                custom_project: str = None
+                repository: GitlabProject = None
+                while custom_project is None:
+                    custom_project = input(
+                        f'Enter path to {student_group.get_name()}\'s repository (leave blank to skip): ')
+                    try:
+                        if len(custom_project) > 0:
+                            repository = GitlabProject(custom_project)
+                    except GitlabError:
+                        print(f'Could not location repository {custom_project}; please confirm path.')
+                        custom_project = None
+                if len(custom_project) > 0:
+                    display_git_contributions(repository)
             else:
                 project_name = f'{project_prefix}{student_group.get_name().split()[1]}'.zfill(zero_padding)
                 display_git_contributions(list(filter(lambda p: p.get_name() == project_name, projects))[0])