Error:


Traceback:
TypeError: Cannot read property 'length' of null
    at Object.acquireContext (http://601452-4832-7d5dff.runbot17.odoo.com/web/static/lib/Chart/Chart.js:6896:19)
    at Chart.construct (http://601452-4832-7d5dff.runbot17.odoo.com/web/static/lib/Chart/Chart.js:8415:26)
    at new Chart (http://601452-4832-7d5dff.runbot17.odoo.com/web/static/lib/Chart/Chart.js:8402:7)
    at Class.render_graph (http://601452-4832-7d5dff.runbot17.odoo.com/web/content/5447-229a005/web.assets_backend.js:8016:904)
    at http://601452-4832-7d5dff.runbot17.odoo.com/web/content/5447-229a005/web.assets_backend.js:8017:57
    at Function._.each._.forEach (http://601452-4832-7d5dff.runbot17.odoo.com/web/content/5446-fc34194/web.assets_common.js:114:558)
    at Class.render_graphs [as _super] (http://601452-4832-7d5dff.runbot17.odoo.com/web/content/5447-229a005/web.assets_backend.js:8016:1961)
    at Class.render_graphs (http://601452-4832-7d5dff.runbot17.odoo.com/web/content/5447-229a005/web.assets_backend.js:9610:573)
    at Class.render_graphs (http://601452-4832-7d5dff.runbot17.odoo.com/web/content/5446-fc34194/web.assets_common.js:3868:371)
    at Class.on_attach_callback (http://601452-4832-7d5dff.runbot17.odoo.com/web/content/5447-229a005/web.assets_backend.js:8015:1640)