Angular Material v6 Mat-Footer - "Cannot read property 'template' of undefined"

You can define your own "tableFooterColumns" variable.

tableFooterColumns: string[] = ['total'];

and use it in the template (change "colspan" for your needs):

 <tr mat-footer-row *matFooterRowDef="tableFooterColumns" colspan="2"></tr>

FIXED: This was not made clear in the material documentation, but all columns must contain a <mat-footer-cell/> element, even if only one column will contain content.