title: How to exclude undefined and null when use filter in Angular Material Table?
body: <p>please help. Is there any way I can exclude the undefined and null from filtering? So, if the cell value is null or undefined it's not being shown when the user types "null" or "undefined" in search input.</p>
  
  <p>Incoming table data:</p>
  
  <pre><code>dataSource: MatTableDataSource
  </code></pre>
  
  <p>The below method is applied on input:</p>
  
  <pre><code>  applyFilter(filterValue: string) {
      this.dataSource.filter = filterValue.trim().toLowerCase();
    }
  </code></pre>