GiveAllItems command don't check if instance is const

[bogu9821]

Only instances/prototypes with the const flag can be used to create a valid object. Items can now be created from instance variables, such as var c_item, which can result in a crash. Add a flag check after the type check and this command and it will work fine. https://github.com/Franisz/zUtilities/blob/583795192ee3df2084bb71a4d6cb547674ff94a7/zUtilities/Commands.cpp#L17#L37