diff --git a/io/previewgenerator.cpp b/io/previewgenerator.cpp
index ea7772e3c..1a0011896 100644
--- a/io/previewgenerator.cpp
+++ b/io/previewgenerator.cpp
@@ -67,7 +67,12 @@ void PreviewGenerator::run() {
                         if (read_ret != AVERROR_EOF) qDebug() << "[ERROR] Failed to read packet for preview generation";
                         break;
                     } else if (codec_ctx[packet.stream_index] != NULL) {
-                        avcodec_send_packet(codec_ctx[packet.stream_index], &packet);
+                        int send_ret = avcodec_send_packet(codec_ctx[packet.stream_index], &packet);
+                        if (send_ret < 0) {
+                            qDebug() << "[ERROR] Failed to send packet for preview generation - aborting";
+                            end_of_file = true;
+                            break;
+                        }
                     }
                 }
                 if (!end_of_file) {
@@ -103,6 +108,9 @@ void PreviewGenerator::run() {
                             s->preview_lock.unlock();
 
                             sws_freeContext(sws_ctx);
+
+                            avcodec_close(codec_ctx[packet.stream_index]);
+                            codec_ctx[packet.stream_index] = NULL;
                         } else if (fmt_ctx->streams[packet.stream_index]->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) {
                             int interval = qFloor((temp_frame->sample_rate/WAVEFORM_RESOLUTION)/4)*4;
 
@@ -175,7 +183,9 @@ void PreviewGenerator::run() {
             }
             av_frame_free(&temp_frame);
             for (unsigned int i=0;i<fmt_ctx->nb_streams;i++) {
-                avcodec_close(codec_ctx[i]);
+                if (codec_ctx[i] != NULL) {
+                    avcodec_close(codec_ctx[i]);
+                }
             }
             delete [] codec_ctx;
         }
diff --git a/panels/project.cpp b/panels/project.cpp
index f0dde2937..0bd57c86e 100644
--- a/panels/project.cpp
+++ b/panels/project.cpp
@@ -183,7 +183,8 @@ void Project::delete_selected_media() {
         Media* m = get_media_from_tree(items.at(i));
         if (!m->is_sequence && sequence != NULL) {
             for (int j=0;j<sequence->clip_count();j++) {
-                if (sequence->get_clip(j)->media == m) {
+                Clip* c = sequence->get_clip(j);
+                if (c != NULL && c->media == m) {
                     remove = false;
                     break;
                 }
diff --git a/ui/timelinewidget.cpp b/ui/timelinewidget.cpp
index ddda9e663..32da1ce03 100644
--- a/ui/timelinewidget.cpp
+++ b/ui/timelinewidget.cpp
@@ -672,6 +672,8 @@ void TimelineWidget::update_ghosts(QPoint& mouse_pos) {
 }
 
 void TimelineWidget::mouseMoveEvent(QMouseEvent *event) {
+    bool alt = (event->modifiers() & Qt::AltModifier);
+
     panel_timeline->cursor_frame = panel_timeline->getFrameFromScreenPoint(event->pos().x());
     panel_timeline->cursor_track = getTrackFromScreenPoint(event->pos().y());
 
@@ -793,7 +795,7 @@ void TimelineWidget::mouseMoveEvent(QMouseEvent *event) {
         for (int i=0;i<sequence->clip_count();i++) {
             Clip* clip = sequence->get_clip(i);
             if (clip != NULL && clip->track == track) {
-                panel_timeline->split_clip_and_relink(clip, panel_timeline->drag_frame_start, !(event->modifiers() & Qt::AltModifier));
+                panel_timeline->split_clip_and_relink(clip, panel_timeline->drag_frame_start, !alt);
 				repaint = true;
 			}
 		}
@@ -828,8 +830,11 @@ void TimelineWidget::mouseMoveEvent(QMouseEvent *event) {
                         !(clip->timeline_in > frame_max && clip->timeline_out > frame_max)) {
                     QVector<Clip*> session_clips;
                     session_clips.append(clip);
-                    for (int j=0;j<clip->linked.size();j++) {
-                        session_clips.append(sequence->get_clip(clip->linked.at(j)));
+
+                    if (!alt) {
+                        for (int j=0;j<clip->linked.size();j++) {
+                            session_clips.append(sequence->get_clip(clip->linked.at(j)));
+                        }
                     }
 
                     for (int j=0;j<session_clips.size();j++) {