Hotjar JS code still displayed when the ID field is left blank

[mvc1095]

If I activate this plugin, enter a Hotjar ID, then return to the settings page and remove the ID, the Hotjar JS snippet will still be printed on the page but with the ID field missing. This is problematic when network activating this plugin for several sites at once in a multisite installation, since I may choose to enable Hotjar for only one or two sites at a time. As a workaround, it's possible to activate this plugin site by site, and then disable to remove it. However, it would better if the plugin could check whether the variable was actually set before printing the JS snippet.