[common] fix 'AttributeError'

fixes regression introduced in 98d3354575

gallery_dl/extractor/common.py

@@ -31,6 +31,7 @@ class Extractor():
     category = ""
     subcategory = ""
     basecategory = ""
+    basesubcategory = ""
     categorytransfer = False
     directory_fmt = ("{category}",)
     filename_fmt = "{filename}.{extension}"
@@ -961,7 +962,6 @@ class AsynchronousMixin():
 
 
 class BaseExtractor(Extractor):
-    basesubcategory = ""
     instances = ()
 
     def __init__(self, match):

gallery_dl/extractor/e621.py

@@ -180,7 +180,6 @@ class E621FavoriteExtractor(E621Extractor):
 class E621FrontendExtractor(Extractor):
     """Extractor for alternative e621 frontends"""
     basecategory = "E621"
-    basesubcategory = ""
     category = "e621"
     subcategory = "frontend"
     pattern = r"(?:https?://)?e621\.(?:cc/\?tags|anthro\.fr/\?q)=([^&#]*)"

gallery_dl/extractor/paheal.py

@@ -15,7 +15,6 @@ from .. import text, exception
 class PahealExtractor(Extractor):
     """Base class for paheal extractors"""
     basecategory = "shimmie2"
-    basesubcategory = ""
     category = "paheal"
     filename_fmt = "{category}_{id}_{md5}.{extension}"
     archive_fmt = "{id}"