void addDiffDetails(Address p1Address, StyledDocument doc) {
		// FUTURE This may need to be changed to a background task.
		if (diffDetails != null) {
			diffDetails.getAllDetails(p1Address, doc, getDiffCountInfo(p1Address));
		}
		else {
			try {
				doc.insertString(doc.getLength(), "Don't have a second program open.",
					new SimpleAttributeSet());
			}
			catch (BadLocationException e) {
				// Shouldn't happen, since adding at end of doc.
			}
		}
	}
Get the second program for the current Diff.

@return the Diff's second program or null if don't currently have a second program associated
        for a Diff.
Ghidra/Features/ProgramDiff/src/main/java/ghidra/app/plugin/core/diff/ProgramDiffPlugin.java