valueflow.cpp: avoid unnecessary object creation in valueFlowFunctionDefaultParameter()

Author: firewave

lib/valueflow.cpp

@@ -5890,11 +5890,12 @@ static void valueFlowFunctionDefaultParameter(const TokenList& tokenlist, const
                 const std::list<ValueFlow::Value> &values = var->nameToken()->tokAt(2)->values();
                 std::list<ValueFlow::Value> argvalues;
                 for (const ValueFlow::Value &value : values) {
+                    if (!value.isKnown())
+                        continue;
                     ValueFlow::Value v(value);
                     v.defaultArg = true;
-                    v.changeKnownToPossible();
-                    if (v.isPossible())
-                        argvalues.push_back(std::move(v));
+                    v.setPossible();
+                    argvalues.push_back(std::move(v));
                 }
                 if (!argvalues.empty())
                     valueFlowInjectParameter(tokenlist, errorLogger, settings, var, scope, argvalues);