QErrorMessage: Reset 'again' check box between each error message

The choice of whether to show a message again is per message,
so when showing a new message we need to reset the check box
back to its default checked state, otherwise the user might
mistakenly dismiss more than the indented message.

[ChangeLog][Widgets] QErrorMessage will now reset the check
box for showing a message again for each new message shown,
as each individual message has its own suppression state.

Pick-to: 6.5 6.5.0
Change-Id: I86d4bb5eabdb5b7a478c03516108a5edf87fcbe3
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

src/widgets/dialogs/qerrormessage.cpp

@@ -358,6 +358,7 @@ bool QErrorMessagePrivate::nextPending()
 #endif
             currentMessage = std::move(message);
             currentType = std::move(type);
+            again->setChecked(true);
             return true;
         }
     }

tests/auto/widgets/dialogs/qerrormessage/tst_qerrormessage.cpp

@@ -70,8 +70,7 @@ void tst_QErrorMessage::dontShowAgain()
     QVERIFY(errorMessageDialog.isVisible());
     checkBox = errorMessageDialog.findChild<QCheckBox*>();
     QVERIFY(checkBox);
-    QVERIFY(!checkBox->isChecked());
-    checkBox->setChecked(true);
+    QVERIFY(checkBox->isChecked());
     errorMessageDialog.close();
 
     errorMessageDialog.showMessage(htmlString);