fix:u8g2编译警告

components/u8g2/luat_lib_u8g2.c

@@ -934,15 +934,12 @@ u8g2.drawGtfontUtf8("啊啊啊",32,0,0)
 static int l_u8g2_draw_gtfont_utf8(lua_State *L) {
     unsigned char buf[128];
     size_t len;
-    int i = 0;
-    uint8_t strhigh,strlow ;
-    uint16_t e,str;
     const char *fontCode = luaL_checklstring(L, 1,&len);
     unsigned char size = luaL_checkinteger(L, 2);
     int x = luaL_checkinteger(L, 3);
     int y = luaL_checkinteger(L, 4);
     for(;;){
-        e = utf8_next((uint8_t)*fontCode);
+        uint16_t e = utf8_next((uint8_t)*fontCode);
         if ( e == 0x0ffff )
         break;
         fontCode++;