V4MD - how to tell if there is structure encryption

[Andrew Sinning]

I'm using V4MD version 1.

I want to add structure encryption to the dbs saved by my product's end 
users.  However, when the product goes to open a db saved by a previous 
version, it would be nice to know this in advance of calling 
SetStructureEncryption.  The problem is that if I call 
SetStructureEncryption using the expected key but the file does not have 
a structure encryption key, ValentinaErrorString() returns "No error".

Is there a strategy that I can use other trial and error?

Thanks.