fix(subsonic): keep placeholder for unknown username when Gravatar is off

The old getAvatar never looked up the user when Gravatar was disabled
(the default), so an unknown username served the placeholder. Restore
that for the unresolvable-user case now that lookup always happens.

server/subsonic/media_retrieval.go

@@ -28,6 +28,11 @@ func (api *Router) GetAvatar(w http.ResponseWriter, r *http.Request) (*responses
 	ctx := r.Context()
 	u, err := api.ds.User(ctx).FindByUsername(username)
 	if err != nil {
+		// Preserve the pre-upload-avatar behaviour: an unresolvable user must not surface
+		// as an error when Gravatar is off, since the old handler never looked it up.
+		if !conf.Server.EnableGravatar {
+			return api.getPlaceHolderAvatar(w, r)
+		}
 		return nil, err
 	}
 	// An uploaded avatar wins regardless of Gravatar settings, so it must be checked first.

server/subsonic/media_retrieval_test.go

@@ -246,11 +246,22 @@ var _ = Describe("MediaRetrievalController", func() {
 			Expect(w.Code).To(Equal(http.StatusOK))
 		})
 
-		It("returns the same error as before for an unknown username", func() {
+		It("returns the same error as before for an unknown username when Gravatar is on", func() {
+			conf.Server.EnableGravatar = true
+
 			_, err := router.GetAvatar(w, newGetRequest("username=ghost"))
 
 			Expect(err).To(MatchError(model.ErrNotFound))
 		})
+
+		It("serves the placeholder for an unknown username when Gravatar is off, as before", func() {
+			conf.Server.EnableGravatar = false
+
+			_, err := router.GetAvatar(w, newGetRequest("username=ghost"))
+
+			Expect(err).ToNot(HaveOccurred())
+			Expect(w.Code).To(Equal(http.StatusOK))
+		})
 	})
 
 	Describe("GetLyrics", func() {