fix bug in crossover: the child from two normal networks should always be normal.

tensorneat/algorithm/neat/gene/node/default.py

@@ -85,11 +85,14 @@ class DefaultNodeGene(BaseNodeGene):
                 (node1[4] != node2[4])
         )
 
-    def forward(self, attrs, inputs):
+    def forward(self, attrs, inputs, is_output_node=False):
         bias, res, act_idx, agg_idx = attrs
 
         z = agg(agg_idx, inputs, self.aggregation_options)
         z = bias + res * z
-        z = act(act_idx, z, self.activation_options)
+
+        # the last output node should not be activated
+        if not is_output_node:
+            z = act(act_idx, z, self.activation_options)
 
         return z