Fix desktop notifications not working when the window is minimized

Blur webview when the main window loses its focus.

CHANGELOG.md

@@ -24,6 +24,10 @@ Release date: TBD
  - Fixed mis-aligned `+` button of tab bar.
  [#541](https://github.com/mattermost/desktop/issues/541)
 
+#### Windows
+ - Fixed desktop notifications not working when the window has been minimized from inactive state.
+ [#522](https://github.com/mattermost/desktop/issues/522)
+
 ---
 
 ## Release v3.7.0

src/main/mainWindow.js

@@ -77,6 +77,7 @@ function createMainWindow(config, options) {
   // Ideally, app should detect that OS is shutting down.
   mainWindow.on('blur', () => {
     saveWindowState(boundsInfoPath, mainWindow);
+    mainWindow.blurWebView();
   });
 
   mainWindow.on('close', (event) => {