fix deadlock with empty args facts in clause/2. git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@2047 b08c6af1-5177-4d33-ba66-4b1c6b8b522a
fix deadlock with empty args facts in clause/2. git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@2047 b08c6af1-5177-4d33-ba66-4b1c6b8b522a