fix(material/datepicker): error due to synchronous change detection

The month view had a `detectChanges` call that was happening inside a `blur` event which ended up causing re-entrant change detection and hitting an assertion in the framework. These changes remove it since it doesn't appear to be necessary anymore.

Fixes #31959.

Author: crisbeto

src/material/datepicker/calendar-body.ts

@@ -615,7 +615,9 @@ export class MatCalendarBody<D = any> implements OnChanges, OnDestroy, AfterView
       const col = cell.getAttribute('data-mat-col');
 
       if (row && col) {
-        return this.rows[parseInt(row)][parseInt(col)];
+        // We need the optional read here, because this can
+        // fire too late when the user is navigating quickly.
+        return this.rows[parseInt(row)]?.[parseInt(col)] || null;
       }
     }
 

src/material/datepicker/month-view.ts

@@ -462,12 +462,6 @@ export class MatMonthView<D> implements AfterContentInit, OnChanges, OnDestroy {
           this._previewEnd = this._getCellCompareValue(dragRange.end);
         }
       }
-
-      // Note that here we need to use `detectChanges`, rather than `markForCheck`, because
-      // the way `_focusActiveCell` is set up at the moment makes it fire at the wrong time
-      // when navigating one month back using the keyboard which will cause this handler
-      // to throw a "changed after checked" error when updating the preview state.
-      this._changeDetectorRef.detectChanges();
     }
   }