Fix potential npe

Author: mjbvz

src/vs/base/parts/ipc/node/ipc.cp.ts

@@ -229,7 +229,9 @@ export class Client implements IChannelClient, IDisposable {
 					console.warn('IPC "' + this.options.serverName + '" crashed with exit code ' + code + ' and signal ' + signal);
 				}
 
-				this.disposeDelayer.cancel();
+				if (this.disposeDelayer) {
+					this.disposeDelayer.cancel();
+				}
 				this.disposeClient();
 				this._onDidProcessExit.fire({ code, signal });
 			});