@Override
	public RegisterValue getDefaultValue(Register register, Address address) {
		AddressSpace space = address.getAddressSpace();

		// if the address is in an overlay then the default value comes from the original space.
		if (space.isOverlaySpace()) {
			address = ((OverlayAddressSpace) space).translateAddress(address, true);
		}
		// there is a weird deleted overlay case that the following code handles - sortof
		else if (space.getType() == AddressSpace.TYPE_UNKNOWN) {
			return new RegisterValue(register);
		}
		return getRegisterValue(register, address, defaultRegisterValueMap);
	}
if the address is in an overlay and we are getting the default value, then get the default
value from the base space, not the overlay space.
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/util/AbstractStoredProgramContext.java