fix(menu,tooltip): Ensure subscription exists before unsubscribing.

Author: trshafer

src/lib/menu/menu-directive.ts

@@ -69,7 +69,9 @@ export class MdMenu implements AfterContentInit, MdMenuPanel, OnDestroy {
   }
 
   ngOnDestroy() {
-    this._tabSubscription.unsubscribe();
+    if (this._tabSubscription) {
+      this._tabSubscription.unsubscribe();
+    }
   }
 
   /**

src/lib/menu/menu.spec.ts

@@ -384,6 +384,12 @@ describe('MdMenu', () => {
 
   });
 
+  describe('destroy', () => {
+    it('does not throw an error on destroy', () => {
+      const fixture = TestBed.createComponent(SimpleMenu);
+      expect(fixture.destroy.bind(fixture)).not.toThrow();
+    });
+  });
 });
 
 @Component({

src/lib/tooltip/tooltip.spec.ts

@@ -398,6 +398,15 @@ describe('MdTooltip', () => {
       expect(tooltipDirective._tooltipInstance).toBeNull();
     }));
   });
+
+  describe('destroy', () => {
+    it('does not throw an error on destroy', () => {
+      const fixture = TestBed.createComponent(BasicTooltipDemo);
+      fixture.detectChanges();
+      delete fixture.componentInstance.tooltip.scrollSubscription;
+      expect(fixture.destroy.bind(fixture)).not.toThrow();
+    });
+  });
 });
 
 @Component({
@@ -413,6 +422,7 @@ class BasicTooltipDemo {
   position: string = 'below';
   message: string = initialTooltipMessage;
   showButton: boolean = true;
+  @ViewChild(MdTooltip) tooltip: MdTooltip;
 }
 
 @Component({

src/lib/tooltip/tooltip.ts

@@ -154,7 +154,9 @@ export class MdTooltip implements OnInit, OnDestroy {
       this._disposeTooltip();
     }
 
-    this.scrollSubscription.unsubscribe();
+    if (this.scrollSubscription) {
+      this.scrollSubscription.unsubscribe();
+    }
   }
 
   /** Shows the tooltip after the delay in ms, defaults to tooltip-delay-show or 0ms if no input */