fix(blob/service): handle absence proof

[vgonkivs]

Fixes #2860

Proof:

[codecov-commenter]

Codecov Report

Merging #2911 (ce3de80) into main (1ae18c9) will decrease coverage by 0.45%.
The diff coverage is 12.50%.

@@            Coverage Diff             @@
##             main    #2911      +/-   ##
==========================================
- Coverage   51.78%   51.34%   -0.45%     
==========================================
  Files         167      167              
  Lines       10806    10812       +6     
==========================================
- Hits         5596     5551      -45     
- Misses       4717     4767      +50     
- Partials      493      494       +1     

Files	Coverage Δ
share/getters/shrex.go	65.55% <100.00%> (ø)
share/eds/utils.go	14.45% <0.00%> (ø)
blob/service.go	67.64% <0.00%> (-4.31%)	⬇️

... and 8 files with indirect coverage changes