Fixes JChess don't start when engines.json was invalid JSon

src/main/java/com/fathzer/jchess/bot/uci/EngineLoader.java

@@ -9,6 +9,7 @@
 import java.util.List;
 import java.util.Set;
 
+import org.json.JSONException;
 import org.json.JSONObject;
 
 import com.fathzer.jchess.bot.Engine;
@@ -46,7 +47,7 @@ public static void init() throws IOException {
 		} else {
 			EngineData[] dummy;
 			try {
-				dummy = TinyJackson.toArray(new JSONObject(Files.readString(PATH)).getJSONArray("engines"), EngineData.class);
+				dummy = readExternalEnginesData();
 			} catch (IOException e) {
 				dummy = new EngineData[0];
 				error = e;
@@ -57,10 +58,18 @@ public static void init() throws IOException {
 			deDuplicateNames(array);
 		}
 		data = Arrays.asList(array);
+		Runtime.getRuntime().addShutdownHook(new Thread(()-> shutdown()));
 		if (error!=null) {
 			throw error;
 		}
-		Runtime.getRuntime().addShutdownHook(new Thread(()-> shutdown()));
+	}
+
+	private static EngineData[] readExternalEnginesData() throws IOException {
+		try {
+			return TinyJackson.toArray(new JSONObject(Files.readString(PATH)).getJSONArray("engines"), EngineData.class);
+		} catch (JSONException e) {
+			throw new IOException(e);
+		}
 	}
 
 	private static void deDuplicateNames(EngineData[] engines) {

src/main/java/com/fathzer/jchess/swing/JChess.java

@@ -95,7 +95,9 @@ protected boolean onStart() {
 			int result = JOptionPane.showConfirmDialog(null,"An error occured while reading the external engine configuration file (data/engines.json).\nWould you like to quit now?", "Engine configuration error",
 		               JOptionPane.YES_NO_OPTION,
 		               JOptionPane.ERROR_MESSAGE);
-			return result!=0;
+			if (result==0) {
+				return false;
+			}
 		}
 		fixSettings();
 		this.game = new GameSession(panel.getGamePanel(), settings);