Enforce crs_matrix type when using tocsr() - #1261

  1 files  ±0    1 suites  ±0   8m 5s ⏱️ + 1m 23s
838 tests ±0  837 ✅ ±0  1 💤 ±0  0 ❌ ±0 
849 runs  ±0  848 ✅ ±0  1 💤 ±0  0 ❌ ±0 

Results for commit 061d781. ± Comparison against earlier commit 817a634.