Fix crash on cancel clip job & correctly handle abortion of stabilize job

src/jobs/jobmanager.cpp

@@ -247,7 +247,10 @@ void JobManager::slotManageCanceledJob(int id)
 {
     qDebug() << "################### JOB canceled: " << id;
     QReadLocker locker(&m_lock);
-    Q_ASSERT(m_jobs.count(id) > 0);
+    if (m_jobs.count(id) == 0) {
+        // Job finished, nothing to do
+        return;
+    }
     if (m_jobs[id]->m_processed) return;
     m_jobs[id]->m_processed = true;
     //m_jobs[id]->m_completionMutex.unlock(); // crashing on Windows

src/jobs/meltjob.cpp

@@ -212,6 +212,8 @@ bool MeltJob::startJob()
     connect(this, &MeltJob::jobCanceled, [&] () {
         m_showFrameEvent.reset();
         m_consumer->stop();
+        m_successful = false;
+        m_done = true;
         return false;
     });
     m_consumer->run();