Google Earth Engine: cumulative iteration of weekly mean anomaly

Question

Using the link here I've managed to calculate a weekly mean anomaly for several regions of interest.

I'm hoping to calculate a cumulative mean anomaly, then work out how many consecutive weeks have been over a specific value (say 1) in the past 12 weeks from a specific date.

I attempted to calculate the cumulative anomaly using the tutorial on the GEE pages (here). However I'm having a few issues.

I calculated a mean for sea surface temperature and calculated daily anomaly using this code

var collection = ee.ImageCollection('NASA/OCEANDATA/MODIS-Aqua/L3SMI')
 .select('sst')

var reference = collection.filterDate('2002-01-01', '2012-12-31')
   .sort('system:time_start', false);

print('reference', reference)

// Compute the mean of the first 10 years.
var mean = reference.mean();

var series = collection.filterDate('2018-01-01', '2018-12- 
31').map(function(image) {
return image.subtract(mean).set('system:time_start', 
image.get('system:time_start'));
});

I then calculated an average weekly anomaly using this code

var startDate = '2018-01-01';
var endDate = '2018-12-31';
var weekDifference = ee.Date(startDate).advance(1, 
'week').millis().subtract(ee.Date(startDate).millis());
var listMap = ee.List.sequence(ee.Date(startDate).millis(), 
 ee.Date(endDate).millis(), weekDifference);


 //function to get a weekly composite
 function getWeeklysstComposite(date) {
   // Only include sst for consistent compositing.
   var sstWeekly = ee.ImageCollection(series)
                  .filterBounds(PB)
                  .filterDate(date, date.advance(1, 'week'))
                  .select('sst');
   var composite = sstWeekly.mean()
                  .set('system:time_start', date.millis(), 'dateYMD', 
 date.format('YYYY-MM-dd'), 
                  'numbImages', sstWeekly.size());
  return composite;
 }

  var sstWeeklyANMLY = 
  ee.ImageCollection.fromImages(listMap.map(function(dateMillis){
   var date = ee.Date(dateMillis);
   return getWeeklysstComposite(date);
   }));

Using the iterate function tutorial I tried to calculate a cumulative mean weekly anomaly

var time0 = reference.first().get('system:time_start');

var first = ee.List([
  ee.Image(0).set('system:time_start', time0).select([0], ['sst'])
]);

 var accumulate = function(image, list) {
 var previous = ee.Image(ee.List(list).get(-1));
 var added = image.add(previous)
    .set('system:time_start', image.get('system:time_start'));
  return ee.List(list).add(added);
};

 var cumulative = ee.ImageCollection(ee.List(sstWeeklyANMLY.iterate(accumulate, first)));

However I'm getting this error

 ImageCollection (Error)
Image.add: If one image has no bands, the other must also have no bands. Got 
0 and 1.

What is going wrong here and how can I then, once I have a cumulative anomaly, calculate how many of the weeks in the preceding 12 preceding a certain date were over a specific threshold (say 4)?

The link to all my code in google earth engine is here