Cannot read property 'config' of null

[BOUAZIZ-Tarek-Omar]

TypeError: Cannot read property 'config' of null
at Class.run (D:\ionic Projects\Ionic-2-Google-Maps-Marker-Cluster-master\node_modules@angular\cli\tasks\serve.js:51:63)
at check_port_1.checkPort.then.port (D:\ionic Projects\Ionic-2-Google-Maps-Marker-Cluster-master\node_modules@angular\cli\commands\serve.js
:123:26)
at
at process._tickCallback (internal/process/next_tick.js:188:7)