private GhidraFileData addFileData(String fileName, LocalFolderItem folderItem,
			FolderItem versionedFolderItem) {
		GhidraFileData fileData =
			new GhidraFileData(this, fileName, folderItem, versionedFolderItem);
		fileDataCache.put(fileName, fileData);
		projectData.updateFileIndex(fileData);
		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