more error adaptive

cps/epub.py

@@ -48,6 +48,7 @@ def get_epub_info(tmp_file_path, original_file_name, original_file_extension):
         else:
             epub_metadata[s] = "Unknown"
     #detect lang need futher modification in web.py /upload
+    try:#maybe dc:language isn't present, less possible but possible
         lang = p.xpath('dc:language/text()', namespaces=ns)[0]
         lang = lang.split('-', 1)[0]
         if len(lang) == 2:
@@ -56,6 +57,8 @@ def get_epub_info(tmp_file_path, original_file_name, original_file_extension):
             epub_metadata['languages'] = isoLanguages.get(part3=lang).name
         else:
             epub_metadata['languages'] = ""
+    except:
+        epub_metadata['languages'] = ""
 
     coversection = tree.xpath("/pkg:package/pkg:manifest/pkg:item[@id='cover-image']/@href", namespaces=ns)
     if len(coversection) > 0: