fix a bug with null options

Author: rileyajones

src/material/autocomplete/autocomplete-trigger.ts

@@ -625,12 +625,12 @@ export class MatAutocompleteTrigger
         {injector: this._environmentInjector},
       );
     });
-    const optionChanges = this.autocomplete.options.changes.pipe(
+    const optionChanges = this.autocomplete.options?.changes.pipe(
       tap(() => this._positionStrategy.reapplyLastPosition()),
       // Defer emitting to the stream until the next tick, because changing
       // bindings in here will cause "changed after checked" errors.
       delay(0),
-    );
+    ) ?? observableOf();
 
     // When the options are initially rendered, and when the option list changes...
     return (

src/material/autocomplete/autocomplete.ts

@@ -307,7 +307,7 @@ export class MatAutocomplete implements AfterContentInit, OnDestroy {
 
   /** Panel should hide itself when the option list is empty. */
   _setVisibility() {
-    this.showPanel = !!this.options.length;
+    this.showPanel = !!this.options?.length;
     this._changeDetectorRef.markForCheck();
   }