gst: Fix device lost notification handling for closed devices

src/CaptureDeviceImpl.cpp

@@ -87,6 +87,8 @@ CaptureDeviceImpl::~CaptureDeviceImpl()
 
     available_output_formats_.clear();
 
+    index_.remove_device_lost(deviceindex_lost_cb);
+
     device_.reset();
 }
 

src/gstreamer-1.0/tcamsrc/gsttcammainsrc.cpp

@@ -341,6 +341,19 @@ static void gst_tcam_mainsrc_device_lost_callback(const tcam::tcam_device_info*
 {
     GstTcamMainSrc* self = (GstTcamMainSrc*)user_data;
 
+    GstState state;
+
+    // wait for 1 seconds max
+    gst_element_get_state(GST_ELEMENT(self), &state, nullptr, 1000000000);
+
+    if (!self->device || state == GST_STATE_NULL)
+    {
+        // device does not exist
+        // or source is null (aka no device exists)
+        // do nothing
+        return;
+    }
+
     if (!self->device->is_streaming_)
     {
         return;
@@ -386,6 +399,8 @@ static bool gst_tcam_mainsrc_init_camera(GstTcamMainSrc* self)
         return false;
     }
 
+    // this cb will automatically be deleted once the device is closed
+    // no need for explicit cleanup
     self->device->device_->register_device_lost_callback(gst_tcam_mainsrc_device_lost_callback,
                                                          self);