Fix for hardcoded fill value for local grid map in trace worker (TGSAI#666)

* Fix sentinel value bug

* Linting

* Use existing fill value maps for consistency

Author: BrianMichell

src/mdio/segy/_workers.py

@@ -27,7 +27,7 @@
 from mdio.builder.schemas.v1.stats import CenteredBinHistogram
 from mdio.builder.schemas.v1.stats import SummaryStatistics
 from mdio.builder.xarray_builder import _get_fill_value
-from mdio.constants import UINT32_MAX
+from mdio.constants import fill_value_map
 
 
 class SegyFileArguments(TypedDict):
@@ -107,7 +107,9 @@ def trace_worker(  # noqa: PLR0913
     region_slices = tuple(region.values())
     local_grid_map = grid_map[region_slices[:-1]]  # minus last (vertical) axis
 
-    not_null = local_grid_map != UINT32_MAX
+    # The dtype.max is the sentinel value for the grid map.
+    # Normally, this is uint32, but some grids need to be promoted to uint64.
+    not_null = local_grid_map != fill_value_map.get(local_grid_map.dtype.name)
     if not not_null.any():
         return None