UX: Don't close the QR code window if the scanned code is of an invalid format

[willezgo]

Sometimes when I try to scan a perfectly valid QR code, the scanner misinterprets the data and returns a string usually composed of numbers like "65923743" instead of "lnbc...", and then the scanning window is closed and an error message appears ("Can't recognize invoice" etc...).

An improvement would be to just ignore invalid scanned data or maybe just briefly flash a red border to indicate a reading error, but keep the scanning window open as the scanner will usually correctly interpret the QR a few milliseconds/seconds later anyway.

This alleviates the need to close the error message and reopen the scanning manually.