private GhidraFolderData addFolderData(String folderName) {
		GhidraFolderData folderData = folderDataCache.get(folderName);
		if (folderData == null) {
			try {
				folderData = new GhidraFolderData(this, folderName);
				folderDataCache.put(folderName, folderData);
			}
			catch (FileNotFoundException e) {
				// ignore
			}
		}
		return folderData;
	}
Create and add new subfolder data object to cache.  Data will not be created
if folder does not exist or an IOException occurs.
@param folderName name of folder to be added
@return folder data or null if folder does not exist
Ghidra/Framework/Project/src/main/java/ghidra/framework/data/GhidraFolderData.java