Angular 无法读取属性'；旗帜'；未定义的

当我运行ng serve时，我得到以下错误

chunk {main} main.js, main.js.map (main) 2.2 kB [initial] [rendered]
chunk {polyfills} polyfills.js, polyfills.js.map (polyfills) 673 bytes [initial] [rendered]
chunk {polyfills-es5} polyfills-es5.js, polyfills-es5.js.map (polyfills-es5) 518 kB [initial] [rendered]
chunk {runtime} runtime.js, runtime.js.map (runtime) 6.15 kB [entry] [rendered]
chunk {styles} styles.js, styles.js.map (styles) 2.31 MB [initial] [rendered]
chunk {vendor} vendor.js, vendor.js.map (vendor) 341 kB [initial] [rendered]
Date: 2020-02-20T13:02:31.697Z - Hash: 338163632aa756e7ed60 - Time: 29669ms
ERROR in Cannot read property 'flags' of undefined

我尝试过很多东西，比如npm更新、ng构建。但一切都不起作用。 我在浏览器上看到以下消息：， 得不到/

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执行ng—版本 给出以下输出

Angular CLI: 9.0.3
Node: 10.15.0
OS: win32 x64

Angular: 9.0.2
... animations, common, compiler, compiler-cli, core, forms
... language-service, platform-browser, platform-browser-dynamic
... router
Ivy Workspace: Yes

Package                           Version
-----------------------------------------------------------
@angular-devkit/architect         0.900.3
@angular-devkit/build-angular     0.900.3
@angular-devkit/build-optimizer   0.900.3
@angular-devkit/build-webpack     0.900.3
@angular-devkit/core              9.0.3
@angular-devkit/schematics        9.0.3
@angular/cdk                      9.0.1
@angular/cli                      9.0.3
@angular/http                     7.2.16
@angular/material                 9.0.1
@ngtools/webpack                  9.0.3
@schematics/angular               9.0.3
@schematics/update                0.900.3
rxjs                              6.5.4
typescript                        3.7.5
webpack                           4.41.6

Pl帮助

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这是否解决了您的问题：有关9.1.5版，请参阅