Reset lastAbortCheck on updateLevel reset

Otherwise we get to a point that the
  if (updateLevel - lastAbortCheck > 10) {
branch is never executed because updateLevel got to 20000 but lastAbortCheck is still at the last value
diff --git a/poppler/Gfx.cc b/poppler/Gfx.cc
index 531acbd..fd40dd9 100644
--- a/poppler/Gfx.cc
+++ b/poppler/Gfx.cc
@@ -38,6 +38,7 @@
 // Copyright (C) 2012, 2013 Fabio D'Urso <fabiodurso@hotmail.it>
 // Copyright (C) 2012 Lu Wang <coolwanglu@gmail.com>
 // Copyright (C) 2014 Jason Crain <jason@aquaticape.us>
+// Copyright (C) 2017 Klarälvdalens Datakonsult AB, a KDAB Group company, <info@kdab.com>. Work sponsored by the LiMux project of the city of Munich
 //
 // To see a description of the changes please see the Changelog file that
 // came with your tarball or type make ChangeLog if you are building from git
@@ -764,6 +765,7 @@
       if (++updateLevel >= 20000) {
 	out->dump();
 	updateLevel = 0;
+	lastAbortCheck = 0;
       }
 
       // did the command throw an exception