Simple Native Android App that fails when back button pressed

gistfile1.txt

#include <jni.h>
#include <errno.h>

#include <EGL/egl.h>
#include <GLES/gl.h>

#include <android/sensor.h>
#include <android/log.h>
#include <android_native_app_glue.h>

#define LOGI(...) ((void)__android_log_print(ANDROID_LOG_INFO, "native-activity", __VA_ARGS__))
#define LOGW(...) ((void)__android_log_print(ANDROID_LOG_WARN, "native-activity", __VA_ARGS__))

struct android_app* app;


static int init_display(){
  const EGLint attribs[] = {
            EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
            EGL_BLUE_SIZE, 8,
            EGL_GREEN_SIZE, 8,
            EGL_RED_SIZE, 8,
            EGL_NONE
    };
    EGLint w, h, dummy, format;
    EGLint numConfigs;
    EGLConfig config;
    EGLSurface surface;
    EGLContext context;

    EGLDisplay display = eglGetDisplay(EGL_DEFAULT_DISPLAY);

    eglInitialize(display, 0, 0);
    eglChooseConfig(display, attribs, &config, 1, &numConfigs);
    eglGetConfigAttrib(display, config, EGL_NATIVE_VISUAL_ID, &format);
    ANativeWindow_setBuffersGeometry(app->window, 0, 0, format);
    surface = eglCreateWindowSurface(display, config, app->window, NULL);
    context = eglCreateContext(display, config, NULL, NULL);

    if (eglMakeCurrent(display, surface, surface, context) == EGL_FALSE) {
        LOGW("Unable to eglMakeCurrent");
        return -1;
    }

    eglQuerySurface(display, surface, EGL_WIDTH, &w);
    eglQuerySurface(display, surface, EGL_HEIGHT, &h);
    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_FASTEST);
    glEnable(GL_CULL_FACE);
    glShadeModel(GL_SMOOTH);
    glDisable(GL_DEPTH_TEST);
    return 0;
}

static int32_t engine_handle_input(struct android_app* app, AInputEvent* event) {
    return 1;
}

static void engine_handle_cmd(struct android_app* app, int32_t cmd) {
  switch (cmd) {
  case APP_CMD_SAVE_STATE:
      break;
  case APP_CMD_INIT_WINDOW:
      if (app->window != NULL) {
          init_display();
      }
      break;
  case APP_CMD_TERM_WINDOW:
      break;
  case APP_CMD_GAINED_FOCUS:
      break;
  case APP_CMD_LOST_FOCUS:
      break;
  }
}

void android_main(struct android_app* state) {
  LOGI("Working");
  app_dummy();
  state->onAppCmd = engine_handle_cmd;
  state->onInputEvent = engine_handle_input;
  app = state;
}