interpreter: broken constructors when ending with a return

[xymus]

With the interpreter, constructors ending with a return create objects of the wrong type. I've got a Bool and an ASCIIFlatString depending on the context, adding a print inside the constructor caused it to return an empty ASCIIFlatString.

Minimal example:

class A
	init
	do
		#print "foo" # Would cause the creation of an ASCIIFlatString instead of Bool
		return
	end
end
print((new A).class_name) # Prints `Bool`