fix nan in ppocrv4 for benchmark (#14072)

* fix nan in ppocrv4 for benchmark

* fix config

configs/det/ch_PP-OCRv4/ch_PP-OCRv4_det_student.yml

@@ -33,6 +33,7 @@ Architecture:
   Head:
     name: DBHead
     k: 50
+    fix_nan: True
 
 Loss:
   name: DBLoss

configs/det/ch_PP-OCRv4/ch_PP-OCRv4_det_teacher.yml

@@ -33,6 +33,7 @@ Architecture:
     name: PFHeadLocal
     k: 50
     mode: "large"
+    fix_nan: True
     
 
 Loss:

ppocr/modeling/heads/det_db_head.py

@@ -32,7 +32,7 @@ def get_bias_attr(k):
 
 
 class Head(nn.Layer):
-    def __init__(self, in_channels, kernel_list=[3, 2, 2], **kwargs):
+    def __init__(self, in_channels, kernel_list=[3, 2, 2], fix_nan=False, **kwargs):
         super(Head, self).__init__()
 
         self.conv1 = nn.Conv2D(
@@ -73,14 +73,16 @@ class Head(nn.Layer):
             bias_attr=get_bias_attr(in_channels // 4),
         )
 
+        self.fix_nan = fix_nan
+
     def forward(self, x, return_f=False):
         x = self.conv1(x)
         x = self.conv_bn1(x)
-        if self.training:
+        if self.fix_nan and self.training:
             x = paddle.where(paddle.isnan(x), paddle.zeros_like(x), x)
         x = self.conv2(x)
         x = self.conv_bn2(x)
-        if self.training:
+        if self.fix_nan and self.training:
             x = paddle.where(paddle.isnan(x), paddle.zeros_like(x), x)
         if return_f is True:
             f = x