由于循环中的字符串到日期转换导致的Rbindlist错误

I'm building a complex code that loops over 10-1000 files, and calculates a whole bunch of summary statistics for each file based on 6 grouping columns. That all works fine, but in the double apply structure, I'm also trying to extract the date from the filename and convert that to a date format, and add it as column to each data frame. I'm building a complex code that loops over 10-