[fix] do not crash if publication date is missing in pubmed engine

searx/engines/pubmed.py

@@ -84,14 +84,17 @@ def response(resp):
                     content = content[0:300] + "..."
         # TODO: center snippet on query term
 
+        res_dict = {'url': url,
+                    'title': title,
+                    'content': content}
+
+        try:
             publishedDate = datetime.strptime(entry.xpath('.//DateCreated/Year')[0].text
                                               + '-' + entry.xpath('.//DateCreated/Month')[0].text
                                               + '-' + entry.xpath('.//DateCreated/Day')[0].text, '%Y-%m-%d')
-
-        res_dict = {'url': url,
-                    'title': title,
-                    'publishedDate': publishedDate,
-                    'content': content}
+            res_dict['publishedDate'] = publishedDate
+        except:
+            pass
 
         results.append(res_dict)