Fixed issue where launching the app a second time wouldn't show the main window if it was hidden. (#2712)

src/main/app/app.ts

@@ -29,6 +29,7 @@ export function handleAppSecondInstance(event: Event, argv: string[]) {
 
     // Protocol handler for win32
     // argv: An array of the second instance’s (command line / deep linked) arguments
+    MainWindow.show();
     const deeplinkingURL = getDeeplinkingURL(argv);
     if (deeplinkingURL) {
         openDeepLink(deeplinkingURL);