Web panel stops working when I add a constructor to the tutorial code

Hello, I’m using the example code for Due Date Indicator web panel: https://developer.atlassian.com/server/jira/platform/adding-content-to-the-jira-view-issue-page/

It works when I run it, but now I’m changing the code to try to figure out how the Group Manager works and how I can use it in my own code.

Since the documentation is really vague and does not provide any concrete examples I’m aware of, I found this code that uses the Group Manager function: https://github.com/alexandrov-d/hide-jira-fields/blob/master/src/main/java/com/adon/nc/hidefields/servlet/ConfigServlet.java

When I add the constructor to my class and compile it - it runs, but the due date indicator stops working and no errors are added to the logs. Also, the addon runs fine in the Addon Management.

Can somebody explain to me why?

package com.example.plugins.tutorial;

import com.atlassian.jira.issue.Issue;
import com.atlassian.jira.plugin.webfragment.contextproviders.AbstractJiraContextProvider;
import com.atlassian.jira.plugin.webfragment.model.JiraHelper;
import com.atlassian.jira.user.ApplicationUser;

import com.atlassian.crowd.embedded.api.Group; // <--- Added to tutorial code to include Group Manager
import com.atlassian.jira.security.groups.GroupManager; // <--- Added to tutorial code to include Group Manager

import java.sql.Timestamp;
import java.time.LocalDate;
import java.util.HashMap;
import java.util.Map;
import java.util.Collection;

import static java.time.temporal.ChronoUnit.DAYS;

public class DueDateIndicator extends AbstractJiraContextProvider {

    private final GroupManager groupManager;

    public DueDateIndicator( // <--- Added to tutorial code to include Group Manager
        GroupManager groupManager
    ){
        this.groupManager = groupManager;
    }

    @Override
    public Map<String, Object> getContextMap(ApplicationUser applicationUser, JiraHelper jiraHelper) {
        Map<String, Object> contextMap = new HashMap<>();
        Issue currentIssue = (Issue) jiraHelper.getContextParams().get("issue");
        Timestamp dueDate = currentIssue.getDueDate();
        if (dueDate != null) {
            LocalDate currentTimeInDays = LocalDate.now();
            LocalDate dueDateTimeInDays = dueDate.toLocalDateTime().toLocalDate();
            long daysAwayFromDueDateCalc = DAYS.between(currentTimeInDays, dueDateTimeInDays);
            contextMap.put("daysAwayFromDueDate", daysAwayFromDueDateCalc);
        }

        int groups = groupManager.getUsersInGroupCount("jira-administrators"); // <--- Added to tutorial code to test Group Manager
        contextMap.put("groups", groups); // <--- Added to tutorial code to test Group Manager

        return contextMap;
    }
}