all: Propagate errors from NamespacedKV (#6203)

As foretold by the prophecy, "once the database refactor is merged, then
shall appear a request to propagate errors from the store known
throughout the land as the NamedspacedKV, and it shall be good".

lib/api/api.go

@@ -769,11 +769,21 @@ func (s *service) getSystemConnections(w http.ResponseWriter, r *http.Request) {
 }
 
 func (s *service) getDeviceStats(w http.ResponseWriter, r *http.Request) {
-	sendJSON(w, s.model.DeviceStatistics())
+	stats, err := s.model.DeviceStatistics()
+	if err != nil {
+		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
+		return
+	}
+	sendJSON(w, stats)
 }
 
 func (s *service) getFolderStats(w http.ResponseWriter, r *http.Request) {
-	sendJSON(w, s.model.FolderStatistics())
+	stats, err := s.model.FolderStatistics()
+	if err != nil {
+		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
+		return
+	}
+	sendJSON(w, stats)
 }
 
 func (s *service) getDBFile(w http.ResponseWriter, r *http.Request) {

lib/api/mocked_model_test.go

@@ -48,12 +48,12 @@ func (m *mockedModel) ConnectionStats() map[string]interface{} {
 	return nil
 }
 
-func (m *mockedModel) DeviceStatistics() map[string]stats.DeviceStatistics {
-	return nil
+func (m *mockedModel) DeviceStatistics() (map[string]stats.DeviceStatistics, error) {
+	return nil, nil
 }
 
-func (m *mockedModel) FolderStatistics() map[string]stats.FolderStatistics {
-	return nil
+func (m *mockedModel) FolderStatistics() (map[string]stats.FolderStatistics, error) {
+	return nil, nil
 }
 
 func (m *mockedModel) CurrentFolderFile(folder string, file string) (protocol.FileInfo, bool) {