Fix TypeError when tvdbseason/TVDBid is None in anime-list mappings

[tsannie]

Problem

Some entries in anime-list-master.xml (ScudLee) have tvdbseason set to None —
notably One Piece (tvdb-81797) which has dozens of AniDB sub-entries. This causes
TypeError: cannot concatenate 'str' and 'NoneType' objects when fetching metadata.

Changes

• TVDBid.isdigit() → (TVDBid or "").isdigit() — guard against None
• 's'+tvdbseason+'e'+... → 's'+str(tvdbseason or '1')+'e'+... — fallback to season 1
  when mapping is absent
• 's'+defaulttvdbseason → 's'+str(defaulttvdbseason or '1') — same concatenation fix
• int(season.get("tvdbseason")) → added is not None guard — int(None) crashes
• Sanitize anime name in SCUDLEE_FEEDBACK.format() to prevent KeyError from curly
  braces in titles