QCborStreamReader: don't assume that clear() results in isNull()

That QString and QByteArray::clear() shed all capacity() is a
historical artifact we will fix at some point. Don't add more code
that assumes a clear()ed string isNull().

Amends 8af346c1f66f813c3c8fe4d8b892ecfbe96eacfb.
Amends 1d9137e13f9eb3f183c967e9e911c5b260f93dc0.

Task-number: QTBUG-31283
Task-number: QTBUG-60745
Pick-to: 6.7
Change-Id: Ib0d929325088d3e8e119fee3eafa964a783dc8e9
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Juha Vuolle <juha.vuolle@qt.io>

1 files changed, 3 insertions, 3 deletions

diff --git a/src/corelib/serialization/qcborstreamreader.h b/src/corelib/serialization/qcborstreamreader.h
index f5e8fd689f..f2bd2a614b 100644
--- a/src/corelib/serialization/qcborstreamreader.h
+++ b/src/corelib/serialization/qcborstreamreader.h
@@ -150,21 +150,21 @@ public:
     {
         QString dst;
         if (!appendToString(dst))
-            dst.clear();
+            dst = QString{};
         return dst;
     }
     QByteArray toUtf8String()
     {
         QByteArray dst;
         if (!appendToUtf8String(dst))
-            dst.clear();
+            dst = QByteArray{};
         return dst;
     }
     QByteArray toByteArray()
     {
         QByteArray dst;
         if (!appendToByteArray(dst))
-            dst.clear();
+            dst = QByteArray{};
         return dst;
     }