script: Put getGuiEngine() inside a client-only #ifdef

src/script/cpp_api/s_base.h

@@ -136,8 +136,10 @@ class ScriptApiBase : protected LuaHelper {
 	Environment* getEnv() { return m_environment; }
 	void setEnv(Environment* env) { m_environment = env; }
 
+#ifndef SERVER
 	GUIEngine* getGuiEngine() { return m_guiengine; }
 	void setGuiEngine(GUIEngine* guiengine) { m_guiengine = guiengine; }
+#endif
 
 	void objectrefGetOrCreate(lua_State *L, ServerActiveObject *cobj);
 
@@ -158,6 +160,8 @@ class ScriptApiBase : protected LuaHelper {
 
 	IGameDef       *m_gamedef = nullptr;
 	Environment    *m_environment = nullptr;
+#ifndef SERVER
 	GUIEngine      *m_guiengine = nullptr;
+#endif
 	ScriptingType  m_type;
 };

src/script/lua_api/l_base.cpp

@@ -62,10 +62,12 @@ Environment *ModApiBase::getEnv(lua_State *L)
 	return getScriptApiBase(L)->getEnv();
 }
 
+#ifndef SERVER
 GUIEngine *ModApiBase::getGuiEngine(lua_State *L)
 {
 	return getScriptApiBase(L)->getGuiEngine();
 }
+#endif
 
 std::string ModApiBase::getCurrentModPath(lua_State *L)
 {

src/script/lua_api/l_base.h

@@ -32,12 +32,12 @@ extern "C" {
 
 #ifndef SERVER
 class Client;
+class GUIEngine;
 #endif
 
 class ScriptApiBase;
 class Server;
 class Environment;
-class GUIEngine;
 
 class ModApiBase : protected LuaHelper {
 
@@ -46,12 +46,13 @@ class ModApiBase : protected LuaHelper {
 	static Server*          getServer(lua_State *L);
 	#ifndef SERVER
 	static Client*          getClient(lua_State *L);
+	static GUIEngine*       getGuiEngine(lua_State *L);
 	#endif // !SERVER
 
 	static IGameDef*        getGameDef(lua_State *L);
 
 	static Environment*     getEnv(lua_State *L);
-	static GUIEngine*       getGuiEngine(lua_State *L);
+
 	// When we are not loading the mod, this function returns "."
 	static std::string      getCurrentModPath(lua_State *L);