fix: batch switch with query parameters

community/www/batch/progress.py

@@ -17,7 +17,7 @@ def get_context(context):
 
 class BatchReport:
     def __init__(self, course, batch):
-        self.submissions = get_submissions(batch)
+        self.submissions = get_submissions(course, batch)
         self.exercises = self.get_exercises(course.name)
         self.submissions_by_exercise = defaultdict(list)
         for s in self.submissions:
@@ -29,8 +29,10 @@ class BatchReport:
     def get_submissions_of_exercise(self, exercise_name):
         return self.submissions_by_exercise[exercise_name]
 
-def get_submissions(batch):
-    students = batch.get_students()
+def get_submissions(course, batch):
+    students = course.get_students(batch.name)
+    if not len(students):
+        return []
     students_map = {s.email: s for s in students}
     names, values = nparams("s", students_map.keys())
     sql = """