fixup: default NNOISE

Author: arunkannawadi

python/lsst/cell_coadds/_fits.py

@@ -411,7 +411,7 @@ def _readSingleCellCoadd(
         """
         buffer = (outer_cell_size - inner_cell_size) // 2
 
-        n_noise_realizations: int = header.get("NNOISE")
+        n_noise_realizations = header.get("NNOISE", 0)
 
         psf = ImageD(
             array=data["psf"].astype(np.float64),