Grading types should not allow empty field for "Total Number" and "Number of Droppable"

STUD-988

cms/static/coffee/spec/models/settings_course_grader_spec.coffee

@@ -18,3 +18,10 @@ define ["js/models/settings/course_grader"], (CourseGrader) ->
                 expect(model.get('weight')).toBe(7)
                 expect(model.get('min_count')).toBe(3)
                 expect(model.get('drop_count')).toBe(1)
+
+            it "gives validation error if min_count is less than 1 or drop_count is NaN", ->
+                model = new CourseGrader()
+                errors = model.validate({min_count: 0, drop_count: ''}, {validate:true})
+                expect(errors.min_count).toBe('Please enter an integer greater than 0.')
+                expect(errors.drop_count).toBe('Please enter an integer.')
+

cms/static/js/models/settings/course_grader.js

@@ -50,16 +50,18 @@ var CourseGrader = Backbone.Model.extend({
                 }
             }}
         if (_.has(attrs, 'min_count')) {
-            if (!isFinite(attrs.min_count) || /\D+/.test(attrs.min_count)) {
-                errors.min_count = gettext("Please enter an integer.");
+            var intMinCount = parseInt(attrs.min_count, 10);
+            if (!isFinite(intMinCount) || /\D+/.test(intMinCount) || intMinCount < 1) {
+                errors.min_count = gettext("Please enter an integer greater than 0.");
             }
-            else attrs.min_count = parseInt(attrs.min_count, 10);
+            else attrs.min_count = intMinCount;
         }
         if (_.has(attrs, 'drop_count')) {
-            if (!isFinite(attrs.drop_count) || /\D+/.test(attrs.drop_count)) {
+            var intDropCount = parseInt(attrs.drop_count, 10);
+            if (!isFinite(intDropCount) || /\D+/.test(intDropCount) || isNaN(intDropCount)) {
                 errors.drop_count = gettext("Please enter an integer.");
             }
-            else attrs.drop_count = parseInt(attrs.drop_count, 10);
+            else attrs.drop_count = intDropCount;
         }
         if (_.has(attrs, 'min_count') && _.has(attrs, 'drop_count') && attrs.drop_count > attrs.min_count) {
             errors.drop_count = _.template(