Merge lp:~chciken/qr-tools/fix-index-error into lp:qr-tools

[Niko Zurstraßen]

Wrapping a try/except block around data_decode.
This fixes segmentation faults which might occur when decoding broken qr codes with a webcam.

This fixes bug #1909309.

[Ramiro Algozino (algozino)]

lgtm. Thank you for taking care of this.

review: Approve

=== modified file 'qtqr.py'
--- qtqr.py	2020-10-24 11:53:42 +0000
+++ qtqr.py	2021-01-08 07:15:30 +0000
@@ -897,15 +897,26 @@
         if device:
             qr = QR()
             qr.decode_webcam(device=device)
-            if qr.data_decode[qr.data_type](qr.data) == 'NULL':
-                QtWidgets.QMessageBox.warning(
-                    self,
-                    self.tr("Decoding Failed"),
-                    self.tr("<p>Oops! no code was found.<br /> Maybe your webcam didn't focus.</p>"),
-                    QtWidgets.QMessageBox.Ok
+            try:
+                matchData = qr.data_decode[qr.data_type](qr.data)
+            except IndexError:
+              QtWidgets.QMessageBox.warning(
+                  self,
+                  self.tr("Decoding Failed"),
+                  self.tr(f"<p>oops! Your code seems to be of type '{qr.data_type}', but no decoding for data '{qr.data}' could be found.</p>"),
+                  QtWidgets.QMessageBox.Ok
                 )
             else:
-                self.showInfo(qr)
+                if matchData == 'NULL':
+                    QtWidgets.QMessageBox.warning(
+                        self,
+                        self.tr("Decoding Failed"),
+                        self.tr("<p>Oops! no code was found.<br /> Maybe your webcam didn't focus.</p>"),
+                        QtWidgets.QMessageBox.Ok
+                  )
+                else:
+                    self.showInfo(qr)
+
             qr.destroy()
 
     def about(self):