Incorrect update of list of rooms during edit entry

To reproduce bug:

• Add/edit entry:
• let's assume you have a area a1 with 4 rooms and a area a2 with only 1 room
• when a1 is selected 4 rooms are able to select
• change to a2 now
• expected: all rooms are removed and room of a2 is displayed
• current result: only first 2 rooms are removed from list and third room is replaced by the room of a2

Problem:

When set option to null in JS the aoption removed imediately and option[1] becomes option[0]. Counting 0..length-1 is incorrect here:

Solution:
Count from last element to first element instead of first to last in lines approx. 390.
Replace corresponding lines in edit_entry.php by:

roomOptionNum = roomsObj.length;
for (i=(roomOptionNum-1); i >= 0 ; i--)
{
roomsObj.options[i] = null
}