script runner cannot invoke method get value () on a null object

[Patricia Pattin]

Getting this error (see attachment) when trying to run this script (see below). Can anyone advise. 

import com.onresolve.scriptrunner.runner.customisers.PluginModule;

import com.onresolve.scriptrunner.runner.customisers.WithPlugin;

@WithPlugin("com.atlassian.teams")

@PluginModule GeneralTeamService teamService;

import com.atlassian.jira.bc.issue.search.SearchService;

import com.atlassian.jira.component.ComponentAccessor;

import com.atlassian.jira.event.type.EventDispatchOption;

import com.atlassian.jira.issue.customfields.manager.OptionsManager;

import com.atlassian.jira.jql.parser.JqlQueryParser;

import com.atlassian.jira.web.bean.PagerFilter;

import com.atlassian.jira.issue.index.IssueIndexingService;

import com.atlassian.jira.issue.Issue;

import com.atlassian.jira.util.ImportUtils;

import com.atlassian.rm.teams.api.team.GeneralTeamService;

import com.atlassian.rm.teams.core.team.data.DefaultTeam;

import org.apache.log4j.Logger

import org.apache.log4j.Level

// Set-up the logging.

def log = Logger.getLogger("com.acme.CreateSubtask")

log.setLevel(Level.DEBUG)

// Set this variable to enable/disable dry run.

def DRY_RUN = false

// Update the filter of issues that we want to update.

def queryString = "(project = NR OR project = NEWRELIC) AND Team = 166";

def currentUser = ComponentAccessor.getJiraAuthenticationContext().getLoggedInUser();

def jqlQueryParser = ComponentAccessor.getComponent(JqlQueryParser);

def searchService = ComponentAccessor.getComponent(SearchService);

def optionsManager = ComponentAccessor.getComponent(OptionsManager);

def customFieldManager = ComponentAccessor.getCustomFieldManager();

def issueManager = ComponentAccessor.issueManager;

def reIndexIssue(Issue issue) {

    boolean wasIndexing = ImportUtils.isIndexIssues();

    ImportUtils.setIndexIssues(true);

    def issueIndexingService = ComponentAccessor.getComponent(IssueIndexingService);

    issueIndexingService.reIndex(issue);

    ImportUtils.setIndexIssues(wasIndexing);

}

def teamField = customFieldManager.getCustomFieldObjectsByName("Team").first();

def gmField = customFieldManager.getCustomFieldObjectsByName("GM Group").first();

def query = jqlQueryParser.parseQuery(queryString);

def search = searchService.search(currentUser, query, PagerFilter.getUnlimitedFilter());

def count = 0

search.results.each{documentIssue ->

    def issue = issueManager.getIssueObject(documentIssue.id);

    // Get team value for this ticket.

    def teamValue = issue.getCustomFieldValue(teamField)

    if (!teamValue) {

        return;

    }

    def teamName = teamValue.getDescription().getTitle()

    // Extract the GM group implied in the name `GM -> Team`

    def splits = teamName.split(" -> ")

    if (splits.size() < 2) {

        return;

    }

    def inferredGmGroup = splits[0]

    def currentGmGroup = issue.getCustomFieldValue(gmField).getValue()

    if (currentGmGroup.equals(inferredGmGroup)) {

        // Ticket is already correct.

        return;

    }

    count++

    // Update the GM Group field in the ticket

    if (!DRY_RUN) {

        def gmConfig = gmField.getRelevantConfig(issue)

        def gmOptions = optionsManager.getOptions(gmConfig)

        issue.setCustomFieldValue(gmField, gmOptions.getOptionForValue(inferredGmGroup, null))

        ComponentAccessor.issueManager.updateIssue(currentUser, issue, EventDispatchOption.ISSUE_UPDATED, false)

        reIndexIssue(issue)

    }

}

log.debug("Issues updated: " + count)

[Nic Brough -Adaptavist-]

There are two things it might be - 

getValue is not a valid call to make on the object being returned by the previous function (which is getCustomFieldValue)

The value in the field is null (the field is empty)