Fixed the bug appearing when there is only one cell for computation

examples/example_cell/data/cell_ids.csv

-uniqueCellIds
+unique_cell_ids
 cell_2423204507
-cell_2423204508

losscalculator/damage_calculator.py

@@ -45,7 +45,7 @@ def get_exposure_per_tile(
     full_ground_motion_field = losslib.get_full_GMF(
         ground_motion_field, lons_whole_area, lats_whole_area, interpolation_method
     )
-    cell_ids = np.loadtxt(cell_id_source_filepath, dtype="str", skiprows=1)
+    cell_ids = pd.read_csv(cell_id_source_filepath)
     with open(result_filepath, "a+", newline="") as write_obj:
         csv_writer = csv.writer(write_obj)
         if exposure_type == "building":
@@ -119,7 +119,7 @@ def get_exposure_per_tile(
             csv_writer.writerow(title)
 
     for i in range(cell_ids.shape[0]):
-        cell_id = cell_ids[i]
+        cell_id = cell_ids.loc[i][0]
 
         exposure_per_tile = exposure.loc[exposure[tile_id] == cell_id]