small improvments to mastery

The credit for each learning objective is the number of passed topics in
that LO divided by the number of topics in that LO. Previously it was
dividing by the number of topics in the whole exam.

The "current topic" progress item isn't shown when the exam is finished.

diagnostic_scripts/mastery.jme

@@ -56,8 +56,8 @@ next_topic (The next topic to assess):
             available_topics,   // Topics that we can move to next: either no dependencies, or all their dependencies have been passed.
                 filter(
                     t -> let(
-                        all_deps_passed, all(topicdict[topicname]["status"]="passed" for: topicname of: t["topic"]["depends_on"]),
-                        all_deps_passed and t["status"]<>"passed"
+                        all_deps_passed, all(topicdict[topicname]["status"] <> "unknown" for: topicname of: t["topic"]["depends_on"]),
+                        all_deps_passed and t["status"]="unknown"
                     )
                     , topics
                 ),
@@ -202,7 +202,7 @@ after_exam_ended (The state after the exam has finished):
 
 progress (Summarise the student's progress through the exam):
     let(
-        passed_topics, filter(t -> t["status"]="passed", state["topics"])
+        passed_topics, filter(t -> t["status"] = "passed", state["topics"])
     ,   num_passed_topics, len(passed_topics)
     ,   num_topics, len(state["topics"])
     ,   exam_progress, num_passed_topics/num_topics
@@ -212,14 +212,14 @@ progress (Summarise the student's progress through the exam):
             let(
                 ltopics, filter(t -> lo["name"] in t["topic"]["learning_objectives"], state["topics"]),
                 passed, filter(t -> t["status"]="passed", ltopics),
-                p, len(passed)/len(topics),
+                p, len(passed)/len(ltopics),
                 ["name": lo["name"], "progress": p, "credit": p]
             )
             for: lo
             of: learning_objectives
     ,   topic_progress, [["name": "Current topic: {current_topic}", "progress": topic_credit, "credit": topic_credit]]
 
-    ,   topic_progress 
+    ,   if(state["finished"], [], topic_progress)
           + lo_progress
           + [
                 ["name": translate("control.total"), "progress": exam_progress, "credit": exam_progress]