It seems the bug is due to a problem with something called WebView which is pre-installed on all Android devices. WebView is a system component powered by Chrome that allows Android apps to display web content. To get your Gmail working again you simply need to download the latest version from the Google Play Store.
Here are full instructions to get things fixed:
• To update Android System WebView and Google Chrome via Google Play:
• Navigate to Play Store app
• Search for Android System WebView (https://play.google.com/store/apps/details?id=com.google.android.webview&hl=en_AU&gl=US)
• Select the “Update” option
Along with Gmail, this glitch also hit users of Google, Amazon and Yahoo! apps.
Once you have installed the latest update from the Play Store things should return to normal.