Better error message when importing charts incorrectly. (#7790)

* Created a better error message when chartjs can't find an element in the DOM.
Also, prevented an exception when trying to find the canvas assuming is an array. When it could also be null.

* Exception is not thrown anymore in getCanvas. Now this pr only prevents the
item.lenght exception and logs a better error when a chart cant be created.

* Deleted error description because i forgot chartjs is used in varois other ways than importing, also used isArray from helpers.core

* isArray check deleted because the type of the dom element received in getCanvas could be not only an array.

Co-authored-by: Lautaro Alonso Urtiaga <lautaro.urtiaga@10pines.com>