* ext/bigdecimal/bigdecimal.c (BigDecimal_divide): Use Qnil and NIL_P
  instead of (VALUE)0 as a return value.

* ext/bigdecimal/bigdecimal.c (BigDecimal_div): ditto.

* ext/bigdecimal/bigdecimal.c (BigDecimal_divremain): ditto.

* ext/bigdecimal/bigdecimal.c (BigDecimal_remainder): ditto.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39885 b2dd03c8-39d4-4d8f-98ff-823fe69b080e