FMU3 (and similar) constructors should probably initialize all fields

[topolarity]

The constructor here:

FMIBase.jl/src/FMI3/struct.jl

Lines 474 to 478 in 2a30f63

	function FMU3(logLevel::FMULogLevel = FMULogLevelWarn)
	inst = new()
	inst.instances = []
	inst.modelName = ""
	inst.logLevel = logLevel

leaves a lot of fields undefined, including many pointer fields that are probably best to explicitly set to C_NULL

Julia does not zero-initialize plain data fields, so these contain garbage data. For example, if someone fails to initialize one of these pointers, it's probably best to guarantee you'll get a NULL pointer de-reference, rather than accessing random memory.

[ThummeTo]

True and will be fixed 👍