fix(select): error when attempting to open before init

Fixes an error that could be thrown by `mat-select` if it is opened before everything is done initializing.

Fixes #8236.

Author: crisbeto

src/lib/select/select.spec.ts

@@ -2559,6 +2559,11 @@ describe('MatSelect', () => {
       expect(label.textContent).toContain('azziP',
           'Expected the displayed text to be "Pizza" in reverse.');
     });
+
+    it('should not throw when attempting to open too early', () => {
+      const fixture = TestBed.createComponent(BasicSelect);
+      expect(() => fixture.componentInstance.select.open()).not.toThrow();
+    });
   });
 
   describe('change event', () => {

src/lib/select/select.ts

@@ -515,7 +515,7 @@ export class MatSelect extends _MatSelectMixinBase implements AfterContentInit,
 
   /** Opens the overlay panel. */
   open(): void {
-    if (this.disabled || !this.options.length) {
+    if (this.disabled || !this.options || !this.options.length) {
       return;
     }
 
@@ -605,7 +605,7 @@ export class MatSelect extends _MatSelectMixinBase implements AfterContentInit,
 
   /** The value displayed in the trigger. */
   get triggerValue(): string {
-    if (!this._selectionModel || this._selectionModel.isEmpty()) {
+    if (this.empty) {
       return '';
     }
 
@@ -912,10 +912,12 @@ export class MatSelect extends _MatSelectMixinBase implements AfterContentInit,
    * the first item instead.
    */
   private _highlightCorrectOption(): void {
-    if (this._selectionModel.isEmpty()) {
-      this._keyManager.setFirstItemActive();
-    } else {
-      this._keyManager.setActiveItem(this._getOptionIndex(this._selectionModel.selected[0])!);
+    if (this._keyManager) {
+      if (this.empty) {
+        this._keyManager.setFirstItemActive();
+      } else {
+        this._keyManager.setActiveItem(this._getOptionIndex(this._selectionModel.selected[0])!);
+      }
     }
   }