Correct handling of a Multilink filterspec with an empty list of linked-to items.

Author: stefanseefeld

roundup/backends/rdbms_common.py

@@ -2206,7 +2206,7 @@ def filter(self, search_matches, filterspec, sort=[], group=[]):
                 if p.sort_type < 2:
                     mlfilt = 1
                     tn = '%s_%s'%(pcn, k)
-                    if v in ('-1', ['-1']):
+                    if v in ('-1', ['-1'], []):
                         # only match rows that have count(linkid)=0 in the
                         # corresponding multilink table)
                         where.append(self._subselect(pcn, tn))