using it.
The crash was due to a null pointer present for select_lex while 
processing the view.
Adding a check while opening the view to see if its a child of a 
merge table fixed this problem.

mysql-test/r/merge.result:
  Updated result for the new test case.
mysql-test/t/merge.test:
  Added test case based on the bug description.
sql/sql_base.cc:
  Added a check to check if the view being opened is a child table of a
  merge table and return error if it is.