QTBUG-57933 Cocoa: Check if charactersIgnoringModifiers is not empty too

If a dead key occurs as a result of pressing a key combination then
characters will have 0 length, but charactersIgnoringModifiers will
have a valid character in it. This enables key combinations such as
ALT+E to be used as a shortcut with an English keyboard even though
pressing ALT+E will give a dead key while doing normal text input.

src/plugins/platforms/cocoa/qnsview.mm

@@ -1574,10 +1574,16 @@ - (void)handleKeyEvent:(NSEvent *)nsevent eventType:(int)eventType
 
     QChar ch = QChar::ReplacementCharacter;
     int keyCode = Qt::Key_unknown;
-    if ([characters length] != 0) {
+
+    // If a dead key occurs as a result of pressing a key combination then
+    // characters will have 0 length, but charactersIgnoringModifiers will
+    // have a valid character in it. This enables key combinations such as
+    // ALT+E to be used as a shortcut with an English keyboard even though
+    // pressing ALT+E will give a dead key while doing normal text input.
+    if ([characters length] != 0 || [charactersIgnoringModifiers length] != 0) {
         if (((modifiers & Qt::MetaModifier) || (modifiers & Qt::AltModifier)) && ([charactersIgnoringModifiers length] != 0))
             ch = QChar([charactersIgnoringModifiers characterAtIndex:0]);
-        else
+        else if ([characters length] != 0)
             ch = QChar([characters characterAtIndex:0]);
         keyCode = [self convertKeyCode:ch];
     }