Merge remote-tracking branch 'upstream/3.4' into merge-3.4

modules/core/src/system.cpp

@@ -1768,7 +1768,7 @@ FLAGS getFlags()
 
 NodeData::NodeData(const char* funName, const char* fileName, int lineNum, void* retAddress, bool alwaysExpand, cv::instr::TYPE instrType, cv::instr::IMPL implType)
 {
-    m_funName       = funName;
+    m_funName       = funName ? cv::String(funName) : cv::String();  // std::string doesn't accept NULL
     m_instrType     = instrType;
     m_implType      = implType;
     m_fileName      = fileName;