From d261640fa7cd2b28cfa40ec53267388d2ab4e5d7 Mon Sep 17 00:00:00 2001
From: Austin Adams <git@austinjadams.com>
Date: Tue, 26 Sep 2023 18:28:20 -0400
Subject: [PATCH] Throw a slightly more friendly message when a student opens
 an empty file

This error gets propagated to autograders, so a more friendly error message is useful
---
 src/main/java/com/ra4king/circuitsim/gui/CircuitSim.java | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/main/java/com/ra4king/circuitsim/gui/CircuitSim.java b/src/main/java/com/ra4king/circuitsim/gui/CircuitSim.java
index d3bf221..cb0802f 100644
--- a/src/main/java/com/ra4king/circuitsim/gui/CircuitSim.java
+++ b/src/main/java/com/ra4king/circuitsim/gui/CircuitSim.java
@@ -1474,6 +1474,9 @@ public void loadCircuits(File file) throws Exception {
 						
 						CircuitFile circuitFile = FileFormat.load(lastSaveFile);
 						
+						if (circuitFile == null) {
+							throw new NullPointerException("File is empty!");
+						}
 						if (circuitFile.circuits == null) {
 							throw new NullPointerException("File missing circuits");
 						}