Fixed crash when moving horizontal slider thumb in preview with no toolpath active

src/slic3r/GUI/GCodeViewer.cpp

@@ -1689,6 +1689,8 @@ void GCodeViewer::refresh_render_paths(bool keep_sequential_current_first, bool
             break;
     }
 
+    unsigned int render_paths_count = 0;
+
     // second pass: filter paths by sequential data and collect them by color
     for (const auto& [buffer, index_buffer_id, path_id] : paths) {
         const Path& path = buffer->paths[path_id];
@@ -1711,6 +1713,7 @@ void GCodeViewer::refresh_render_paths(bool keep_sequential_current_first, bool
             it->color = color;
             it->path_id = path_id;
             it->index_buffer_id = index_buffer_id;
+            ++render_paths_count;
         }
 
         unsigned int segments_count = std::min(m_sequential_view.current.last, path.last.s_id) - std::max(m_sequential_view.current.first, path.first.s_id) + 1;
@@ -1733,6 +1736,8 @@ void GCodeViewer::refresh_render_paths(bool keep_sequential_current_first, bool
         it->offsets.push_back(static_cast<size_t>((path.first.i_id + delta_1st) * sizeof(unsigned int)));
     }
 
+    wxGetApp().plater()->enable_preview_moves_slider(render_paths_count > 0);
+
 #if ENABLE_GCODE_VIEWER_STATISTICS
     for (const TBuffer& buffer : m_buffers) {
         m_statistics.render_paths_size += SLIC3R_STDVEC_MEMSIZE(buffer.render_paths, RenderPath);