Align TensorFlow and OpenCV paths to create a text graph

samples/dnn/tf_text_graph_common.py

@@ -323,7 +323,7 @@ def writeTextGraph(modelPath, outputPath, outNodes):
 
             for node in graph_def.node:
                 if node.op == 'Const':
-                    if 'value' in node.attr:
-                        del node.attr['value']
+                    if 'value' in node.attr and node.attr['value'].tensor.tensor_content:
+                        node.attr['value'].tensor.tensor_content = ''
 
         tf.train.write_graph(graph_def, "", outputPath, as_text=True)