Fixed bug #27362: crash at evaluation of IN predicate when one
of its argument happened to be a decimal expression returning
the NULL value.
The crash was due to the fact the function in_decimal::set did
not take into account that val_decimal() could return 0 if 
the decimal expression had been evaluated to NULL.  


mysql-test/r/func_in.result:
  Added a test case for bug #27362.
mysql-test/t/func_in.test:
  Added a test case for bug #27362.
sql/item_cmpfunc.cc:
  Fixed bug #27362: crash at evaluation of IN predicate when one
  of its argument happened to be a decimal expression returning
  the NULL value.
  The crash was due to the fact the function in_decimal::set did
  not take into account that val_decimal() could return 0 if 
  the decimal expression had been evaluated to NULL.