Log uncaught errors / promise rejections in main process

See #2019.

main.js

@@ -1,3 +1,4 @@
+const addUnhandledErrorHandler = require('electron-unhandled');
 const path = require('path');
 const url = require('url');
 const os = require('os');
@@ -22,6 +23,16 @@ const logging = require('./app/logging');
 const windowState = require('./app/window_state');
 const { createTemplate } = require('./app/menu');
 
+addUnhandledErrorHandler({
+  logger: (error) => {
+    console.log(
+      'main.js: Uncaught error or unhandled promise rejection:',
+      error && error.stack ? error.stack : error
+    );
+  },
+  showDialog: false,
+});
+
 const appUserModelId = `org.whispersystems.${packageJson.name}`;
 console.log('Set Windows Application User Model ID (AUMID)', { appUserModelId });
 app.setAppUserModelId(appUserModelId);