Bug#11764671  57533: UNINITIALISED VALUES IN COPY_AND_CONVERT (SQL_STRING.CC) WITH CERTAIN CHA
When ROUND evaluates decimal result it uses Item::decimal
value as fraction value for the result. In some cases
Item::decimal is greater than real result fraction value
and uninitialised memory of result(decimal) buffer can be
used in further calculations. Issue is introduced by
Bug33143 fix. The fix is to remove erroneous assignment.


mysql-test/r/func_math.result:
  test case
mysql-test/t/func_math.test:
  test case
sql/item_func.cc:
  remove erroneous assignment