MDL-42777 courses: removed unneeded category check

On course view manage page, JS was not getting initalised as category-listing
is not visible, initialiseCourses is doing unnessary check for category as
it takes care of empty category so it should not return on empty category

course/yui/build/moodle-course-management/moodle-course-management-debug.js

@@ -281,10 +281,6 @@ Console.prototype = {
         if (!listing) {
             return false;
         }
-        if (!category) {
-            Y.log('Couldn\'t find the current category object.', 'warn', 'moodle-course-management');
-            return false;
-        }
         listing.all('.listitem[data-id]').each(function(node){
             this.registerCourse(new Course({
                 node : node,

course/yui/build/moodle-course-management/moodle-course-management.js

@@ -278,9 +278,6 @@ Console.prototype = {
         if (!listing) {
             return false;
         }
-        if (!category) {
-            return false;
-        }
         listing.all('.listitem[data-id]').each(function(node){
             this.registerCourse(new Course({
                 node : node,

course/yui/src/management/js/console.js

@@ -279,10 +279,6 @@ Console.prototype = {
         if (!listing) {
             return false;
         }
-        if (!category) {
-            Y.log('Couldn\'t find the current category object.', 'warn', 'moodle-course-management');
-            return false;
-        }
         listing.all('.listitem[data-id]').each(function(node){
             this.registerCourse(new Course({
                 node : node,