throw exception when team not found

service/src/main/java/com/telephoners/krakyournet/ctf/exceptions/TeamNotFoundException.java

+package com.telephoners.krakyournet.ctf.exceptions;
+
+import javax.ws.rs.WebApplicationException;
+import javax.ws.rs.core.Response;
+
+public class TeamNotFoundException extends WebApplicationException
+{
+    public TeamNotFoundException() {
+    super(Response.status(Response.Status.NOT_FOUND)
+        .entity("Team not found.").type("text/plain").build());
+    }
+}

service/src/main/java/com/telephoners/krakyournet/ctf/repositories/TeamsRepository.java

@@ -2,6 +2,7 @@ package com.telephoners.krakyournet.ctf.repositories;
 
 import com.telephoners.krakyournet.ctf.beans.Team;
 import com.telephoners.krakyournet.ctf.beans.User;
+import com.telephoners.krakyournet.ctf.exceptions.TeamNotFoundException;
 import org.mongodb.morphia.Datastore;
 
 import javax.inject.Inject;
@@ -27,7 +28,8 @@ public class TeamsRepository extends Repository<Team>
     {
         return datastore.createQuery(Team.class).asList().stream()
                 .filter(team -> team.getMembers().contains(user))
-                .findFirst().get();
+                .findFirst()
+                .orElseThrow(TeamNotFoundException::new);
     }
 
     public Team getTeamByUserName(String username)