fix(tooltip): error when updating position while closed (#10704)

Fixes an error that is being thrown when opening a tooltip, closing it and updating its position.

Author: crisbeto

src/lib/tooltip/tooltip.spec.ts

@@ -321,6 +321,33 @@ describe('MatTooltip', () => {
       expect(tooltipDirective._overlayRef!.updatePosition).toHaveBeenCalled();
     }));
 
+    it('should not throw when updating the position for a closed tooltip', fakeAsync(() => {
+      tooltipDirective.position = 'left';
+      tooltipDirective.show(0);
+      fixture.detectChanges();
+      tick();
+
+      tooltipDirective.hide(0);
+      fixture.detectChanges();
+      tick();
+
+      // At this point the animation should be able to complete itself and trigger the
+      // _animationDone function, but for unknown reasons in the test infrastructure,
+      // this does not occur. Manually call the hook so the animation subscriptions get invoked.
+      tooltipDirective._tooltipInstance!._animationDone({
+        fromState: 'visible',
+        toState: 'hidden',
+        totalTime: 150,
+        phaseName: 'done',
+      } as AnimationEvent);
+
+      expect(() => {
+        tooltipDirective.position = 'right';
+        fixture.detectChanges();
+        tick();
+      }).not.toThrow();
+    }));
+
     it('should be able to modify the tooltip message', fakeAsync(() => {
       assertTooltipInstance(tooltipDirective, false);
 

src/lib/tooltip/tooltip.ts

@@ -120,7 +120,11 @@ export class MatTooltip implements OnDestroy {
 
       if (this._overlayRef) {
         this._updatePosition();
-        this._tooltipInstance!.show(value, 0);
+
+        if (this._tooltipInstance) {
+          this._tooltipInstance!.show(value, 0);
+        }
+
         this._overlayRef.updatePosition();
       }
     }