Remove two blank error log statements in the default error handler

[mpvosseller]

The default error handler calls console.error() (with no arguments) twice.

koa/lib/application.js

Line 204 in 9ee6584

console.error();

Unfortunately this causes some confusing noise in AWS Lambda + CloudWatch which shows these as "ERROR undefined" log entries

Would you consider a PR to do one of the following:

• simply remove these two error statements
• remove these two empty statements AND add two \n inside the call console.error(msg.replace(/^/gm, ' '));
• add an option to skip the log statements

Thanks

[mpvosseller]

For context this is what it looks like in AWS CloudWatch when viewing the error log. Each console.error() statement causes a log entry. So each invocation of the default error handler causes three entries when the first and last are useless noise.

[mpvosseller]

See PR #1471 which implements the second option above.