fix terminal component modeler

Author: tylerflex

tidy3d/plugins/smatrix/component_modelers/terminal.py

@@ -316,8 +316,8 @@ def compute_power_wave_amplitudes_at_each_port(
         for port_out in self.ports:
             V_out, I_out = self.compute_port_VI(port_out, sim_data)
             indexer = {"port": port_out.name}
-            V_matrix.loc[indexer] = V_out
-            I_matrix.loc[indexer] = I_out
+            V_matrix = V_matrix._with_updated_data(data=V_out.data, coords=indexer)
+            I_matrix = I_matrix._with_updated_data(data=I_out.data, coords=indexer)
 
         V_numpy = V_matrix.values
         I_numpy = I_matrix.values