chore: Minor code improvements

- Changed variable name in `get_content` function
- Added proper exceptions for `get_topic` and `get_content` functions in lms
diff --git a/erpnext/public/js/education/lms/components/Article.vue b/erpnext/public/js/education/lms/components/Article.vue
index 4678db2..eab1424 100644
--- a/erpnext/public/js/education/lms/components/Article.vue
+++ b/erpnext/public/js/education/lms/components/Article.vue
@@ -32,7 +32,7 @@
     methods: {
         getContent() {
             return lms.call('get_content', {
-                type: this.type,
+                content_type: this.type,
                 content: this.content
             })
         }
diff --git a/erpnext/public/js/education/lms/components/Video.vue b/erpnext/public/js/education/lms/components/Video.vue
index 2d791bd..29d973a 100644
--- a/erpnext/public/js/education/lms/components/Video.vue
+++ b/erpnext/public/js/education/lms/components/Video.vue
@@ -55,7 +55,7 @@
     methods: {
         getContent() {
             return lms.call('get_content', {
-                type: this.type,
+                content_type: this.type,
                 content: this.content
             })
         }
diff --git a/erpnext/www/lms.py b/erpnext/www/lms.py
index 801d766..4416244 100644
--- a/erpnext/www/lms.py
+++ b/erpnext/www/lms.py
@@ -291,13 +291,15 @@
 # Functions to get program & course details
 @frappe.whitelist(allow_guest=True)
 def get_topics(course_name):
-	course = frappe.get_doc('Course', course_name)
-	topics = course.get_topics()
-	return topics
+	try:
+		course = frappe.get_doc('Course', course_name)
+		return course.get_topics()
+	except frappe.DoesNotExistError:
+		frappe.throw(_("Course {0} does not exist.".format(course_name)))
 
 @frappe.whitelist()
-def get_content(type, content):
+def get_content(content_type, content):
 	try:
-		return frappe.get_doc(type, content)
-	except:
-		return None
\ No newline at end of file
+		return frappe.get_doc(content_type, content)
+	except frappe.DoesNotExistError:
+		frappe.throw(_("{0} {1} does not exist.".format(content_type, content)))
\ No newline at end of file