QHostInfo::abortLookup: ignore -1

The id -1 is the one of a default-constructed QHostInfo (invalid).
It's also returned by various codepaths to mean a lookup failure.
Attemping to abort its lookup should simply be ignored.

Change-Id: I0413dd248a890f57195e4f5b5baea011b6737102
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/network/kernel/qhostinfo.cpp

@@ -998,6 +998,9 @@ void QHostInfoLookupManager::abortLookup(int id)
     if (wasDeleted)
         return;
 
+    if (id == -1)
+        return;
+
 #if QT_CONFIG(thread)
     // is postponed? delete and return
     for (int i = 0; i < postponedLookups.size(); i++) {