Electron: Reverted to older Sharp version to fix Ubuntu issue

ElectronClient/app/app.js

@@ -354,6 +354,11 @@ class Application extends BaseApplication {
 	}
 
 	updateTray() {
+		// Tray icon (called AppIndicator) doesn't work in Ubuntu
+		// http://www.webupd8.org/2017/04/fix-appindicator-not-working-for.html
+		// Might be fixed in Electron 18.x but no non-beta release yet.
+		if (!shim.isWindows() && !shim.isMac()) return;
+
 		const app = bridge().electronApp();
 
 		if (app.trayShown() === Setting.value('showTrayIcon')) return;

ElectronClient/app/package.json

@@ -34,7 +34,8 @@
       "asar": false
     },
     "linux": {
-      "asar": false
+      "asar": false,
+      "category": "Office"
     }
   },
   "homepage": "https://github.com/laurent22/joplin#readme",
@@ -79,7 +80,7 @@
     "react-dom": "^16.0.0",
     "react-redux": "^5.0.6",
     "redux": "^3.7.2",
-    "sharp": "^0.18.4",
+    "sharp": "^0.17.3",
     "smalltalk": "^2.5.1",
     "sprintf-js": "^1.1.1",
     "sqlite3": "^3.1.13",