In most cases, en empty block represents a missing implementation:

if (something) { // Non-Compliant
  // What ?
}

if (something) { // Compliant
  doSomething();
}

for (var i = 0; i < length; i++) { // Non-Compliant
  // Empty on purpose or missing piece of code ?
}

for (var i = 0; i < length; i++) { // Compliant
  doSomething();
}