🐛 fix incompatibility with sphinx conf

docs/source/conf.py

@@ -43,14 +43,14 @@ templates_path = ['templates']
 source_suffix = ''
 
 # The master toctree document.
-master_doc = ''
+master_doc = 'index'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
 #
 # This is also used if you do content translation via gettext catalogs.
 # Usually you set "language" from the command line for these cases.
-language = ''
+language = 'en'
 
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.