Fixed overloaded ‘unique_ptr(NULL)’ is ambiguous errors on cc7

scheduler/ArchiveMount.cpp

@@ -87,7 +87,7 @@ std::unique_ptr<cta::ArchiveJob> cta::ArchiveMount::getNextJob() {
   // try and get a new job from the DB side
   std::unique_ptr<cta::SchedulerDatabase::ArchiveJob> dbJob(m_dbMount->getNextJob().release());
   if (!dbJob.get())
-    return std::unique_ptr<cta::ArchiveJob>(NULL);
+    return std::unique_ptr<cta::ArchiveJob>();
   // We have something to archive: prepare the response
   std::unique_ptr<cta::ArchiveJob> ret(new ArchiveJob(*this, m_ns,
       dbJob->archiveFile, dbJob->remoteFile, dbJob->nameServerTapeFile));

scheduler/RetrieveMount.cpp

@@ -74,7 +74,7 @@ std::unique_ptr<cta::RetrieveJob> cta::RetrieveMount::getNextJob() {
   // Try and get a new job from the DB
   std::unique_ptr<cta::SchedulerDatabase::RetrieveJob> dbJob(m_dbMount->getNextJob().release());
   if (!dbJob.get())
-    return std::unique_ptr<cta::RetrieveJob>(NULL);
+    return std::unique_ptr<cta::RetrieveJob>();
   // We have something to retrieve: prepare the response
   std::unique_ptr<cta::RetrieveJob> ret (new RetrieveJob(*this, 
     dbJob->archiveFile, dbJob->remoteFile, dbJob->nameServerTapeFile,