don't open second window on app restart when in dock mode (fixes #2449)

app/lib/window.ts

@@ -5,6 +5,7 @@ import ElectronConfig = require('electron-config')
 import * as os from 'os'
 import * as path from 'path'
 
+import { parseArgs } from './cli'
 import { loadConfig } from './config'
 
 let SetWindowCompositionAttribute: any
@@ -210,6 +211,12 @@ export class Window {
         }
     }
 
+    handleSecondInstance (argv: string[], cwd: string): void {
+        if (!this.configStore.appearance?.dock) {
+            this.send('host:second-instance', parseArgs(argv, cwd), cwd)
+        }
+    }
+
     private setupWindowManagement () {
         this.window.on('show', () => {
             this.visible.next(true)