private boolean hasValidStartAddress() {
		if (startAddr != null) {
			return true;
		}
		message = "Please enter a valid Start Address";
		if (addressErrorMessage != null) {
			message = "Invalid Address: " + addressErrorMessage;
		}
		return false;
	}
Model to manage adding a memory block.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/memory/AddBlockModel.java