sql: fix possible undefined behavior during cast

This patch fixes possible undefined behavior during the implicit cast of
INTEGER to DOUBLE. The problem is, if the INTEGER is close enough to
2^64, it will be cast to 2^64 when it is cast to DOUBLE. Since we have a
check for loss of precision, this will cause this DOUBLE to be cast to
an INTEGER, which will result in undefined behavior since this DOUBLE is
outside the range of INTEGER.