Fix initial accumulator value for builtin_sum_rows

This a fixup for https://github.com/apache/couchdb-couch/pull/229.
The initial value for accumulator suppose to be 0. Since the result of
sum and count is integer. The problem was discovered by dialyzer.

COUCHDB-3305
1 file changed
tree: 23892318d9ca35411b5f42ef178da1fe3d4328af
  1. .gitignore
  2. .travis.yml
  3. LICENSE
  4. include/
  5. priv/
  6. rebar.config.script
  7. src/
  8. test/