Fix verbose log when stdout/stderr encoding is `None`

See: 5c10453827

yt_dlp/YoutubeDL.py

@@ -3588,7 +3588,7 @@ class YoutubeDL(object):
             return
 
         def get_encoding(stream):
-            ret = getattr(stream, 'encoding', 'missing (%s)' % type(stream).__name__)
+            ret = str(getattr(stream, 'encoding', 'missing (%s)' % type(stream).__name__))
             if not supports_terminal_sequences(stream):
                 from .compat import WINDOWS_VT_MODE
                 ret += ' (No VT)' if WINDOWS_VT_MODE is False else ' (No ANSI)'