fix if logic in dygraph, test=develop (#24209)

python/paddle/fluid/dygraph/nn.py

@@ -961,7 +961,7 @@ class Linear(layers.Layer):
         tmp = self._helper.create_variable_for_type_inference(self._dtype)
         self._helper.append_op(
             type="matmul", inputs=inputs, outputs={"Out": tmp}, attrs=attrs)
-        if self.bias:
+        if self.bias is not None:
             pre_activation = self._helper.create_variable_for_type_inference(
                 dtype=self._dtype)
             self._helper.append_op(

python/paddle/fluid/layers/loss.py

@@ -473,7 +473,7 @@ def edit_distance(input,
         label = erased_label
 
     this_inputs = {"Hyps": [input], "Refs": [label]}
-    if input_length and label_length:
+    if input_length is not None and label_length is not None:
         this_inputs['HypsLength'] = [input_length]
         this_inputs['RefsLength'] = [label_length]
 

python/paddle/fluid/layers/nn.py

@@ -1022,7 +1022,7 @@ def chunk_eval(input,
 
     this_input = {"Inference": [input], "Label": [label]}
 
-    if seq_length:
+    if seq_length is not None:
         this_input["SeqLength"] = [seq_length]
 
     helper.append_op(