C++SDL2尝试渲染SDL_Texture时出错:无效纹理

我正在尝试制作一个简单的游戏，当我尝试渲染SDL_Texture时，我遇到了一个莫名其妙的错误。我已经把一切都设置好了，我能够用SDL_RenderClear成功地清除屏幕，而且我的纹理不是空的，所以它应该被正确创建。但当我尝试调用render()函数时，我得到了一个错误，SDL_GetError()返回"无效纹理"。

编辑：我现在已经按照要求创建了一个MCVE，我对它进行了测试，以验证它是否再现了错误。它应该在窗口中显示路径为"gfx/grid.bmp"的图像，但它却给了我错误。这是完整的MCVE:

#include <SDL.h>
#include <string>
#include <iostream>
#undef main
class Texture{
private:
    SDL_Texture* texture;
    SDL_Renderer* renderer;
    int width;
    int height;
public:
    Texture(){
        texture = nullptr;
    }
    Texture (SDL_Renderer* ren, std::string path){
        texture = nullptr;
        SDL_Surface* surface = nullptr;
        surface = SDL_LoadBMP(path.c_str());
        if(surface == nullptr) return;
        renderer = ren;
        texture = SDL_CreateTextureFromSurface( renderer, surface );
        if(texture == 0) return;
        width = surface->w;
        height = surface->h;
        SDL_FreeSurface(surface);
        std::cout << "Texture '" << path << "' successfully loadedn";
    }
    bool loaded(){
        return texture != 0;
    }
    bool render(int x = 0, int y = 0){
        SDL_Rect dest;
        dest.x = x;
        dest.y = y;
        dest.w = width;
        dest.h = height;
        return SDL_RenderCopy(renderer, texture, nullptr, &dest) == 0;
    }
    void unload(){
        if(loaded()){
            SDL_DestroyTexture(texture);
            texture = nullptr;
            renderer = nullptr;
            width = 0;
            height = 0;
        }
    }
    ~Texture(){
        unload();
    }
};
class CApp{
private:
    bool running = true;
    SDL_Window* window = nullptr;
    SDL_Renderer* renderer = nullptr;
    Texture graphic_grid;
    bool render = true;
public:
    int OnExecute();
    bool OnInit();
    void OnEvent(SDL_Event* event);
    void OnRender();
    void OnCleanup();
};
bool CApp::OnInit(){
    if(SDL_Init(SDL_INIT_EVERYTHING) < 0){
        return false;
    }
    if((window = SDL_CreateWindow("Simple Tic-Tac-Toe", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 600, 600, SDL_WINDOW_SHOWN)) == nullptr){
        return false;
    }
    renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);
    if(renderer == nullptr){
        std::cout << "Renderer failed to load! Error: " << SDL_GetError();
        return false;
    }
    SDL_SetRenderDrawColor( renderer, 0xFF, 0xFF, 0xFF, 0xFF );
    graphic_grid = Texture(renderer, "gfx/grid.bmp");
    if(!graphic_grid.loaded()){
        std::cout << "Image failed to load! Error: " << SDL_GetError();
        return false;
    }
    std::cout << "Initialized fullyn";
    return true;
}
void CApp::OnEvent(SDL_Event* event){
    switch(event->type == SDL_QUIT){
        running = false;
    }
}
void CApp::OnRender(){
    if(!render) return;
    if(SDL_RenderClear(renderer) == 0){
        std::cout << "Successfully cleared screenn";
    }
    if(!graphic_grid.loaded()){
        std::cout << "Texture not loaded!n";
    }else{
        std::cout << "Texture not null!n";
    }
    //This is the place where I get the "Invalid texture" error, everything else works fine
    if(!graphic_grid.render()){
        std::cout << "Failed to render image! Error: " << SDL_GetError() << 'n';
    }
    SDL_RenderPresent(renderer);
    render = false;
}
void CApp::OnCleanup(){
    graphic_grid.unload();
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    renderer = nullptr;
    window = nullptr;
    SDL_Quit();
}
int CApp::OnExecute(){
    if(OnInit() == false){
        return -1;
    }
    SDL_Event event;
    while(running){
        while(SDL_PollEvent(&event)){
            OnEvent(&event);
        }
        OnRender();
    }
    OnCleanup();
    return 0;
}
int main(){
    CApp theApp;
    return theApp.OnExecute();
}

我四处搜索，找不到任何解释我的错误的东西。我能找到的最接近的东西是这个问题，但这个错误是由渲染器在纹理之前被破坏引起的，而我的情况并非如此。

我真的希望有人能告诉我是什么导致了这个错误，任何建议都将不胜感激！