Fix: NullPointerException

src/com/sheepit/client/Client.java

@@ -32,6 +32,7 @@ import java.util.Calendar;
 import java.util.Date;
 import java.util.Observable;
 import java.util.Observer;
+import java.util.Optional;
 import java.util.Random;
 import java.util.Timer;
 import java.util.TimerTask;
@@ -637,10 +638,12 @@ import lombok.Data;
 			// Insert the info at the beginning of the error log
 			writer.write(logHeader.toString().getBytes());
 			
-			ArrayList<String> logs = this.log.getForCheckPoint(step_);
-			for (String line : logs) {
-				writer.write(line.getBytes());
-				writer.write('\n');
+			Optional<ArrayList<String>> logs = this.log.getForCheckPoint(step_);
+			if (logs.isPresent()) {
+				for (String line : logs.get()) {
+					writer.write(line.getBytes());
+					writer.write('\n');
+				}
 			}
 			
 			writer.close();

src/com/sheepit/client/Log.java

@@ -25,6 +25,7 @@ import java.util.ArrayList;
 import java.util.Date;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Optional;
 
 public class Log {
 	private static Log instance = null;
@@ -94,8 +95,8 @@ public class Log {
 		return this.lastCheckPoint;
 	}
 	
-	public ArrayList<String> getForCheckPoint(int point_) {
-		return this.checkpoints.get(point_);
+	public Optional<ArrayList<String>> getForCheckPoint(int point_) {
+		return Optional.ofNullable(this.checkpoints.get(point_));
 	}
 	
 	public void removeCheckPoint(int point_) {
@@ -119,9 +120,11 @@ public class Log {
 	
 	public static synchronized void printCheckPoint(int point_) {
 		Log log = Log.getInstance(null);
-		ArrayList<String> logs = log.getForCheckPoint(point_);
-		for (String alog : logs) {
-			System.out.println(alog);
+		Optional<ArrayList<String>> logs = log.getForCheckPoint(point_);
+		if (logs.isPresent()) {
+			for (String alog : logs.get()) {
+				System.out.println(alog);
+			}
 		}
 	}
 }