CHG: allow nulls in binding logs to support binding by system (not teacher)

db/migrations/stored/R__functions.sql

@@ -1018,7 +1018,8 @@ BEGIN
     DECLARE EXIT HANDLER FOR SQLEXCEPTION RETURN -3;
 
     # todo: move to php layer
-    IF  NOT InternalIsTeacherBound(pTeacherID, pDisciplineID) OR InternalIsMapLocked(pDisciplineID) THEN
+    IF (pTeacherID IS NOT NULL AND NOT InternalIsTeacherBound(pTeacherID, pDisciplineID))
+       OR InternalIsMapLocked(pDisciplineID) THEN
         RETURN -1;
     END IF;
 
@@ -1045,7 +1046,8 @@ CREATE FUNCTION UnbindGroup (
 NO SQL
 BEGIN
     # todo: move to php layer
-    IF NOT InternalIsTeacherBound(pTeacherID, pDisciplineID) OR InternalIsMapLocked(pDisciplineID) THEN
+    IF (pTeacherID IS NOT NULL AND NOT InternalIsTeacherBound(pTeacherID, pDisciplineID))
+       OR InternalIsMapLocked(pDisciplineID) THEN
         RETURN -1;
     END IF;
 
@@ -1070,7 +1072,7 @@ BEGIN
     DECLARE EXIT HANDLER FOR SQLEXCEPTION RETURN -1;
 
     # todo: move to php layer
-    IF NOT InternalIsTeacherBound(pTeacherID, pDisciplineID) THEN
+    IF pTeacherID IS NOT NULL AND NOT InternalIsTeacherBound(pTeacherID, pDisciplineID) THEN
         RETURN -1;
     END IF;
 
@@ -1110,7 +1112,7 @@ BEGIN
     DECLARE EXIT HANDLER FOR SQLEXCEPTION RETURN -1;
 
     # todo: move to php layer
-    IF  NOT InternalIsTeacherBound(pTeacherID, pDisciplineID) THEN
+    IF pTeacherID IS NOT NULL AND NOT InternalIsTeacherBound(pTeacherID, pDisciplineID) THEN
         RETURN -1;
     END IF;
 

db/migrations/structure/V2_0_4_5__allow_bind_by_system.sql

+START TRANSACTION;
+
+ALTER TABLE `logs_binds_groups`
+    CHANGE COLUMN `TeacherID` `TeacherID` INT(11) NULL;
+
+ALTER TABLE `logs_binds_students`
+  CHANGE COLUMN `TeacherID` `TeacherID` INT(11) NULL;
+
+COMMIT ;