fixed non-const call

dune/tectonic/io/io-handler.hh

@@ -85,7 +85,7 @@ class IOHandler {
     }
 
     template <class ProgramState, class GlobalFriction>
-    void write(const ProgramState& programState, const ContactNetwork& contactNetwork, GlobalFriction& friction, const IterationRegister& iterationCount, bool initial = false) {
+    void write(const ProgramState& programState, const ContactNetwork& contactNetwork, const GlobalFriction& friction, const IterationRegister& iterationCount, bool initial = false) {
       if (writeData_) {
         writeData(programState, contactNetwork, friction, iterationCount, initial);
       }