Given that the file size is 776kb, I would suggest that this file has a single volume, and is either a b=0 image or a derived image (TRACE, ADC, etc). It is clumsy that BIDS requires a bvec/bval file for these non-directional images. This is a duplicate of a previous issue and you can therefore use the inheritance principle to add a single bvec file ( a text file with three rows, each with 0) and a single bval file (a text file with a single character, 0) in the top level of your BIDS folder. The Stroke Outcome Optimization Project (SOOP) on OpenNeuro illustrates this solution.
See also related Github and neurostars issues