private GhidraFileData addFileData(String fileName) throws IOException {
		GhidraFileData fileData = fileDataCache.get(fileName);
		if (fileData == null) {
			try {
				fileData = new GhidraFileData(this, fileName);
				fileDataCache.put(fileName, fileData);
				projectData.updateFileIndex(fileData);
			}
			catch (FileNotFoundException e) {
				// ignore
			}
		}
		return fileData;
	}
Create and add new file data object to cache.  Data will not be created
if file does not exist or an IOException occurs.
@param fileName name of file
@return file data or null if not found
@throws IOException if an IO error occurs while checking for file existance
Ghidra/Framework/Project/src/main/java/ghidra/framework/data/GhidraFolderData.java