content adapter: Fix server crash on partial edit

Fixes #12538

hugolib/hugo_sites_build.go

@@ -239,6 +239,10 @@ func (h *HugoSites) process(ctx context.Context, l logg.LevelLogger, config *Bui
 	l = l.WithField("step", "process")
 	defer loggers.TimeTrackf(l, time.Now(), nil, "")
 
+	if _, err := h.init.layouts.Do(ctx); err != nil {
+		return err
+	}
+
 	if len(events) > 0 {
 		// This is a rebuild
 		return h.processPartial(ctx, l, config, init, events)
@@ -324,10 +328,6 @@ func (h *HugoSites) render(l logg.LevelLogger, config *BuildCfg) error {
 		loggers.TimeTrackf(l, start, h.buildCounters.loggFields(), "")
 	}()
 
-	if _, err := h.init.layouts.Do(context.Background()); err != nil {
-		return err
-	}
-
 	siteRenderContext := &siteRenderContext{cfg: config, multihost: h.Configs.IsMultihost}
 
 	i := 0
@@ -918,7 +918,6 @@ func (h *HugoSites) processPartial(ctx context.Context, l logg.LevelLogger, conf
 	if tmplChanged || i18nChanged {
 		// TODO(bep) we should split this, but currently the loading of i18n and layout files are tied together. See #12048.
 		h.init.layouts.Reset()
-
 		if err := loggers.TimeTrackfn(func() (logg.LevelLogger, error) {
 			// TODO(bep) this could probably be optimized to somehow
 			// only load the changed templates and its dependencies, but that is non-trivial.
@@ -991,6 +990,10 @@ func (s *Site) handleContentAdapterChanges(bi pagesfromdata.BuildInfo, buildConf
 }
 
 func (h *HugoSites) processContentAdaptersOnRebuild(ctx context.Context, buildConfig *BuildCfg) error {
+	// Make sure the layouts are initialized.
+	if _, err := h.init.layouts.Do(context.Background()); err != nil {
+		return err
+	}
 	g := rungroup.Run[*pagesfromdata.PagesFromTemplate](ctx, rungroup.Config[*pagesfromdata.PagesFromTemplate]{
 		NumWorkers: h.numWorkers,
 		Handle: func(ctx context.Context, p *pagesfromdata.PagesFromTemplate) error {