Fixed null pointer dereference

src/main/java/de/thm/arsnova/entities/LoggedIn.java

@@ -122,7 +122,7 @@ public class LoggedIn {
 	}
 	
 	public boolean hasConflicts() {
-		return ! (_conflicts == null && _conflicts.isEmpty());
+		return ! (_conflicts == null || _conflicts.isEmpty());
 	}
 
 	@Override