Placing block crashes the website if `Campaign Monitor` module turned on but `Campaign Monitor Campaign` isn't

Steps to replicate

• Turn on `Campaign Monitor` module
• Place a `Campaign Monitor` block on the page
• Head to the page and receive the following error message

Error: Call to undefined function Drupal\campaignmonitor\Plugin\Block\campaignmonitor_campaign_get_campaigns() in Drupal\campaignmonitor\Plugin\Block\CampaignMonitorCampaignBlock->build()