[svn r14117] More fixes to avoid SQL errors when handling a wrongly-removed-course

Returning null so the calling script (mySpace/index.php) knows when there has been a problem

main/inc/lib/tracking.lib.php

@@ -181,6 +181,8 @@ class Tracking {
 		// get the informations of the course 
 		$a_course = CourseManager :: get_course_information($course_code);
 
+		if(!empty($a_course['db_name']))
+		{		
 			// table definition
 			$tbl_course_lp_view = Database :: get_course_table(TABLE_LP_VIEW, $a_course['db_name']);
 			$tbl_course_lp_view_item = Database :: get_course_table(TABLE_LP_ITEM_VIEW, $a_course['db_name']);
@@ -212,6 +214,11 @@ class Tracking {
 	
 			return $avg_progress;
 		}
+		else
+		{
+			return null;
+		}
+	}
 
 	function get_avg_student_score($student_id, $course_code) {
 		
@@ -219,6 +226,8 @@ class Tracking {
 		$course_user_table = Database :: get_main_table(TABLE_MAIN_COURSE_USER);
 		$table_session_course_user = Database :: get_main_table(TABLE_MAIN_SESSION_COURSE_USER);
 		$course = CourseManager :: get_course_information($course_code);
+		if(!empty($course['db_name']))
+		{
 			$lp_table = Database :: get_course_table(TABLE_LP_MAIN,$course['db_name']);
 			$lp_item_table = Database  :: get_course_table(TABLE_LP_ITEM,$course['db_name']);
 			$lp_view_table = Database  :: get_course_table(TABLE_LP_VIEW,$course['db_name']);
@@ -311,6 +320,11 @@ class Tracking {
 	
 			return $pourcentageScore;
 		}
+		else
+		{
+			return null;
+		}
+	}
 
 	/**
 	 * gets the list of students followed by coach
@@ -590,6 +604,8 @@ class Tracking {
 		// get the informations of the course 
 		$a_course = CourseManager :: get_course_information($course_code);
 
+		if(!empty($a_course['db_name']))
+		{
 			// table definition
 			$tbl_item_property = Database :: get_course_table(TABLE_ITEM_PROPERTY, $a_course['db_name']);
 			$sql = 'SELECT 1
@@ -600,6 +616,11 @@ class Tracking {
 			$rs = api_sql_query($sql, __LINE__, __FILE__);
 			return mysql_num_rows($rs);
 		}
+		else
+		{
+			return null;
+		}
+	}
 
 	function count_student_messages($student_id, $course_code) {
 		require_once (api_get_path(LIBRARY_PATH) . 'course.lib.php');
@@ -624,7 +645,7 @@ class Tracking {
 		}
 		else
 		{
-			return 0;
+			return null;
 		}
 	}