Handle SDL event 0x304 by doing nothing (#3670)

components/sdlutil/sdlinputwrapper.cpp

@@ -108,6 +108,11 @@ InputWrapper::InputWrapper(SDL_Window* window, osg::ref_ptr<osgViewer::Viewer> v
                 case SDL_TEXTINPUT:
                     mKeyboardListener->textInput(evt.text);
                     break;
+
+#if SDL_VERSION_ATLEAST(2, 0, 4)
+                case SDL_KEYMAPCHANGED:
+                    break;
+#endif
                 case SDL_JOYHATMOTION: //As we manage everything with GameController, don't even bother with these.
                 case SDL_JOYAXISMOTION:
                 case SDL_JOYBUTTONDOWN:

components/sdlutil/sdlinputwrapper.hpp

@@ -6,6 +6,7 @@
 #include <osg/ref_ptr>
 
 #include <SDL_events.h>
+#include <SDL_version.h>
 
 #include "OISCompat.hpp"
 #include "events.hpp"