這個錯誤是由項目首次打開時，enter/leave時找不到元素而報的一個錯誤。目前還沒找到解決辦法。但對運行還是無關緊要的。
ERROR Error: Unable to process animations due to the following failed trigger transitions
@routeAnimations has failed due to:
-
query(":leave")returned zero elements. (Usequery(":leave", { optional: true })if you wish to allow this.) -
query(":leave")returned zero elements. (Usequery(":leave", { optional: true })if you wish to allow this.)at TransitionAnimationEngine.push…/node_modules/@angular/animations/fesm5/browser.js.TransitionAnimationEngine.reportError (vendor.js:4296)
at TransitionAnimationEngine.push…/node_modules/@angular/animations/fesm5/browser.js.TransitionAnimationEngine._flushAnimations (vendor.js:4442)
at TransitionAnimationEngine.push…/node_modules/@angular/animations/fesm5/browser.js.TransitionAnimationEngine.flush (vendor.js:4262)
at InjectableAnimationEngine.push…/node_modules/@angular/animations/fesm5/browser.js.AnimationEngine.flush (vendor.js:5110)
at vendor.js:133984
at ZoneDelegate.push…/node_modules/zone.js/dist/zone.js.ZoneDelegate.invoke (polyfills.js:7430)
at Zone.push…/node_modules/zone.js/dist/zone.js.Zone.run (polyfills.js:7180)
at NgZone.push…/node_modules/@angular/core/fesm5/core.js.NgZone.runOutsideAngular (vendor.js:79992)
at AnimationRendererFactory.push…/node_modules/@angular/platform-browser/fesm5/animations.js.AnimationRendererFactory.end (vendor.js:133982)
at DebugRendererFactory2.push…/node_modules/@angular/core/fesm5/core.js.DebugRendererFactory2.end (vendor.js:86674)