Merge pull request opencv#17849 from dkurt:fix_17848

Author: alalek

modules/dnn/src/graph_simplifier.cpp

@@ -63,9 +63,6 @@ int Subgraph::getInputNodeId(const Ptr<ImportGraphWrapper>& net,
 {
     CV_Assert(inpId < node->getNumInputs());
     std::string name = node->getInputName(inpId);
-    // If operation produces several tensors, they are specified by index
-    // after ':' character. In example, "input:0".
-    name = name.substr(0, name.rfind(':'));
     const int numNodes = net->getNumNodes();
     for (int i = 0; i < numNodes; ++i)
     {

modules/dnn/src/tensorflow/tf_graph_simplifier.cpp

@@ -31,7 +31,10 @@ class TFNodeWrapper : public ImportNodeWrapper
 
     virtual std::string getInputName(int idx) const CV_OVERRIDE
     {
-        return node->input(idx);
+        // If operation produces several tensors, they are specified by index
+        // after ':' character. In example, "input:0".
+        std::string name = node->input(idx);
+        return name.substr(0, name.rfind(':'));
     }
 
     virtual std::string getType() const CV_OVERRIDE