private boolean ignoreNull(T t) {
		if (t != null) {
			return false;
		}

		if (!allowsNulls) {
			return true;
		}

		if (!isAtEnd()) {
			// null values can only go at the end (see javadoc)
			return true;
		}

		if (historyStack.peek() == null) {
			// no repeated nulls
			return true;
		}

		return false;
	}
Returns the number of items in this history list

@return the number of items in this history list
Ghidra/Framework/Generic/src/main/java/util/HistoryList.java