Fix uninitialized member

Non-static class member "domainIndex" was not initialized in the
constructor nor in any functions that it calls.

Change-Id: Ie72d997a1f0cf2f3499aac6f7714c7a9d3c7d525
Coverity-Id: 174997
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>

src/network/access/qhsts_p.h

@@ -85,8 +85,7 @@ private:
 
     struct DomainLabel
     {
-        DomainLabel() = default;
-        DomainLabel(const QString &name) : label(name) { }
+        DomainLabel(const QString &name = QString()) : label(name), domainIndex(0) {}
 
         bool operator < (const DomainLabel &rhs) const
         { return label < rhs.label; }