FileEditor: avoid useless loading of files of open (but not yet loaded) tabs on app exit

src/main/java/org/markdownwriterfx/FileEditor.java


		private void activated() {
		+ if( tab.getTabPane() == null \|\| !tab.isSelected())
		+ return; // tab is already closed or no longer active
		+
		if (tab.getContent() != null) {
		markdownEditorPane.requestFocus();

Delta	3 lines added, 0 lines removed, 3-line increase