Schema composer allows restrictions on attributes with NULL lower- and upperboun

[Geert Bellekens]

Details:
Sometimes the lowerbound and upperbound columns in t_attribute are left NULL.
The default multiplicity for an attribute is [1..1]
In the schema composer, you can restrict the multiplicity of an attribute, but only to be more strict. I can change a [0..*] into a [0..1], but I'm not allowed to change a [1..1] into a [1..*].
Unless, the lowerbound and upperbound values are NULL. In that case the schema composer allows me to set any type of restriction.
An XMI import/export updates the NULL values to '1'


Steps to Reproduce:
- Create a new schema
- Drag an element into the schema that has an attribute where the lowerbound and upperbound columns are NULL
- Select the option to restrict the attribute
- Notice that you are allowed to change the multiplicity to [1..*] (which is not allowed when the lowerbound and upperbound values are set to '1')

Tested on v16.1

Reported

Geert