For PHOTOSHOP CC 2014 - September+
I took out the whole Prefix and just replaced "FileNamePrefix;" with "layerName;". Then commented out the other two lines with // (Double slashes)
1020 var fileNameBody = layerName;
1021 //fileNameBody += "_" + zeroSuppress(i, 4);
1022 //fileNameBody += "_" + layerName;