void programClosed(Program program) {
		boolean hasProgram = (plugin.getCurrentProgram() != null);
		openCloseDiffViewAction.setEnabled(hasProgram && !plugin.isTaskInProgress());
	}
Called to adjust the Program Diff's actions when a program is closed.
@param program the closed program
Ghidra/Features/ProgramDiff/src/main/java/ghidra/app/plugin/core/diff/DiffActionManager.java