An invalid assertion in Item_direct_view_ref::eq caused 
an assertion abort in the debug version.


mysql-test/r/view.result:
  Added a test case for bug #18386.
mysql-test/t/view.test:
  Added a test case for bug #18386.
sql/item.cc:
  Fixed bug #18386.
  An invalid assertion in Item_direct_view_ref::eq caused 
  an assertion abort in the debug version.
  Changed the assertion.