There's no way. It seems that it is simply impossible to end this type of bug on iOS. We have seen similar problems happening many times. In the most recent, commented by us less than a month ago, a malicious link crashed Messages on both iOS and macOS, this problem was fixed in iOS 11.2.5.
For this week, a new one was discovered. Upon receiving a specific character, iPhone simply locks and blocks access to apps like Messaging, Twitter, WhatsApp, Facebook Messenger, Outlook and Gmail (depending on where you received the message).
The news was shared by the Italian website MobileWorld (Google Translate) and corroborated by The Verge, which confirmed the problem on an iPhone running the latest iOS.
Another iOS bug is crashing iPhones and disabling access to iMessage https://t.co/9do0xyz7k4 pic.twitter.com/15Ripq7PP8
– Tom Warren (@tomwarren) February 15, 2018
Another iOS bug is locking iPhones and disabling access to iMessage. www.theverge.com/2018/2/15/17015654/apple-iphone-crash-ios-11-bug-imessage
As we can see in the videos above, just receive the Indian character (Telugu language) that SpringBoard hangs. If you receive the message in the Messages app, for example, you will no longer be able to open it since it will be unsuccessfully trying to load the character. Apparently, the only way to regain access to the app is to ask someone to send some other message and try to delete the conversation that contains that character. I used the example in Messages but, as I said above, several apps suffer from this same bug and in some the problem can be much more difficult to solve.
Still according to the The Verge, the bug appears to have already been fixed in iOS 11.3. The only thing, however, is that this new version of the system should still take a while to be released, so by then, we will have to "live with" it.
For these and others that iOS 12 has everything to come even focused on polishing and general improvements
Update 02/15/2018 s 13:59
The bug also affects macOS High Sierra 10.13.3 but, as in the case of iOS, it has already been fixed in the latest beta version of macOS 10.13.4.
Update II 02/15/2018 s 18:40
As we said, the bug has already been fixed in both the latest beta versions of iOS 11.3 and macOS 10.13.4. However, taking into account that these updates should still take a long time to reach the hands of users of iPhones / iPads and Macs, Apple confirmed to the The Verge you want to release a fix for the problem before releasing such updates.
That is, prepare for the iOS 11.2.6 and for some macOS security update.