public void setAllowNulls(boolean allowNulls) {
		this.allowsNulls = allowNulls;
	}
True signals that the client allows null items to be used.  When this is true, a null
value will be stored in this list <b>only as the last item</b>.  See the javadoc for 
more info.

@param allowNulls true to allow nulls; the default is false
Ghidra/Framework/Generic/src/main/java/util/HistoryList.java