check if there is a match at all

pymdownx/snippets.py

@@ -104,7 +104,7 @@ def extract_regex(self, regex, lines):
             regex = re.match(r'^/(.*)/$', regex).group(1) # remove the slashes
             for line in lines:
                 m = re.match(regex, line) 
-                if m.groups():
+                if m and m.groups():
                     new_lines.append(" ".join(re.match(nregex, line).groups())) # join the groups together
                 elif m:
                     new_lines.append(line)