GLib event dispatcher: fix iteration in source check in error case

It was accessing the deleted current element in a potentially
reallocated container.

Change-Id: I81d86410907b7b0c20c2edc62ad256315606bc96
Reviewed-by: Andreas Hartmetz <ahartmetz@gmail.com>
Reviewed-by: David Faure <david.faure@kdab.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/kernel/qeventdispatcher_glib.cpp

@@ -86,9 +86,10 @@ static gboolean socketNotifierSourceCheck(GSource *source)
                      p->pollfd.fd, t[int(p->socketNotifier->type())]);
             // ### note, modifies src->pollfds!
             p->socketNotifier->setEnabled(false);
+            i--;
+        } else {
+            pending = ((p->pollfd.revents & p->pollfd.events) != 0);
         }
-
-        pending = ((p->pollfd.revents & p->pollfd.events) != 0);
     }
 
     return pending;