Fixes problem with crop-tgrid

The function xr_crop_tgrid_data was failing tests. The issue has been identified and fixed. This implements the fix from !25.

pyicon/pyicon_calc_xr.py

@@ -792,7 +792,7 @@ def xr_calc_rot_coeff(ds_IcD):
     """
     curl_coeffs = (
         ds_IcD["edge_orientation"]
-        * ds_IcD["dual_edge_length"].isel(edge=ds_IcD["edges_of_vertex"])
+        * ds_IcD["dual_edge_length"].isel(edge=ds_IcD["edges_of_vertex"].compute())
         / ds_IcD["dual_area"]
     )
     return curl_coeffs
@@ -835,5 +835,7 @@ def xr_calc_curl(ds_IcD, vector, rot_coeff=None):
     if rot_coeff is None:
         rot_coeff = xr_calc_rot_coeff(ds_IcD)
 
-    curl_vec = (vector.isel(edge=ds_IcD["edges_of_vertex"]) * rot_coeff).sum(dim="ne_v")
+    curl_vec = (vector.isel(edge=ds_IcD["edges_of_vertex"].compute()) * rot_coeff).sum(
+        dim="ne_v"
+    )
     return curl_vec