Fix watch filtering from subscription feed when watch history is empty

src/invidious.cr

@@ -1948,8 +1948,13 @@ get "/feed/subscriptions" do |env|
           # Show latest video from a channel that a user hasn't watched
           # "unseen_only" isn't really correct here, more accurate would be "unwatched_only"
 
+          if user.watched.empty?
+            values = "'{}'"
+          else
+            values = "VALUES #{user.watched.map { |id| %(('#{id}')) }.join(",")}"
+          end
           videos = PG_DB.query_all("SELECT DISTINCT ON (ucid) * FROM #{view_name} WHERE \
-          NOT id = ANY (VALUES #{user.watched.map { |id| %(('#{id}')) }.join(",")}) \
+          NOT id = ANY (#{values}) \
           ORDER BY ucid, published #{sort}", as: ChannelVideo)
         else
           # Show latest video from each channel
@@ -1963,8 +1968,13 @@ get "/feed/subscriptions" do |env|
         if preferences.unseen_only
           # Only show unwatched
 
+          if user.watched.empty?
+            values = "'{}'"
+          else
+            values = "VALUES #{user.watched.map { |id| %(('#{id}')) }.join(",")}"
+          end
           videos = PG_DB.query_all("SELECT * FROM #{view_name} WHERE \
-          NOT id = ANY (VALUES #{user.watched.map { |id| %(('#{id}')) }.join(",")}) \
+          NOT id = ANY (#{values}) \
           ORDER BY published #{sort} LIMIT $1 OFFSET $2", limit, offset, as: ChannelVideo)
         else
           # Sort subscriptions as normal