Improve armar7 platform movement

source/RobotAPI/components/units/RobotUnit/NJointControllers/NJointHolonomicPlatformVelocityControllerWithRamp.cpp

@@ -160,7 +160,7 @@ namespace armarx
                << oldState << "\ndelta:\n"
                << delta << "\nfactor: " << factor << "\n====\n";
             std::string s = ss.str();
-            ARMARX_RT_LOGF_IMPORTANT("%s", s);
+            ARMARX_RT_LOGF_IMPORTANT("%s", s.c_str());
 
             //                throw LocalException("haeee");
             //            }