Improvements
Checking size of array before retrieving value from it
Commerce day of Iceland is computed, not hardcoded
Checking if end date and type are available
Checking if price is available
Changing course app by new specs
Making yes/no required for some applications
Changing according the latest specs
Removed needless message
Maintaining parameters, showing custom header for error
Maintaining parameters
Providing course's name
Using course's name
Using course's name
Changing by the specs.
Using generics
Changing by specs
Added style classes for text areas
Printing error in SQL query
Double checking if info about child is available