Fix infinite loop on NULL

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>

zathura/completion.c

@@ -294,11 +294,11 @@ cc_bookmarks(girara_session_t* session, const char* input)
 
 error_free:
 
-  if (completion) {
+  if (completion != NULL) {
     girara_completion_free(completion);
   }
 
-  if (group) {
+  if (group != NULL) {
     girara_completion_group_free(group);
   }
 

zathura/marks.c

@@ -160,6 +160,7 @@ cmd_marks_delete(girara_session_t* session, girara_list_t* argument_list)
 
   GIRARA_LIST_FOREACH(argument_list, char*, iter, key_string)
   if (key_string == NULL) {
+    girara_list_iterator_next(iter);
     continue;
   }