dataarray_to_matrix: Make sure that the returned region/inc is a list of scalar values

Author: seisman

pygmt/clib/conversion.py

@@ -124,6 +124,8 @@ def dataarray_to_matrix(grid):
         grid = grid.sortby(variables=list(grid.dims), ascending=True)
 
     matrix = as_c_contiguous(grid[::-1].to_numpy())
+    region = region.tolist()
+    inc = inc.tolist()
     return matrix, region, inc