void first() {
		if (p1LastDiffs.isEmpty()) {
			return;
		}
		goTo(p1LastDiffs.getMinAddress());
	}
Called from the dialog when the cursor should move to the first difference.
Update the buttons in the dialog according to whether there is
a next or previous.
Ghidra/Features/ProgramDiff/src/main/java/ghidra/app/plugin/core/diff/DiffController.java