After adding #PathVariable, resources become unreachable - spring

Question

#GetMapping("/instructor-edit-course")
private String instructorAddCourse(Model model) {
model.addAttribute("course", new Course());
return "instructor-edit-course";
}
Above code is ok. Resources are found.
But when I add #PathVariable to the path like below code, application searches resources in
http://localhost:8080/instructor-edit-course/assets/images/icon/footer/facebook-square#2x.png
instead of
http://localhost:8080/assets/images/icon/footer/facebook-square#2x.png
#GetMapping("/instructor-edit-course/{id}")
private String instructorEditCourse(#PathVariable String id, Model model) {
// go to course page
Course course = courseService.findById(Integer.parseInt(id));
model.addAttribute("course", course);
return "instructor-edit-course";
}
WebConfig class
package com.hrglob.elearning.config;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Description;
import org.springframework.web.servlet.ViewResolver;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.ViewControllerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import org.thymeleaf.spring5.SpringTemplateEngine;
import org.thymeleaf.spring5.view.ThymeleafViewResolver;
import org.thymeleaf.templateresolver.ClassLoaderTemplateResolver;
#Configuration
#EnableWebMvc
#ComponentScan(basePackages = {"com.xxxx.*"})
public class WebConfig implements WebMvcConfigurer {
#Override
public void addViewControllers(ViewControllerRegistry registry) {
registry.addViewController("/").setViewName("index");
}
#Override
public void addResourceHandlers(ResourceHandlerRegistry registry) {
registry.addResourceHandler("/assets/**")
.addResourceLocations("/public", "classpath:/static/", "classpath:/static/assets/")
.setCachePeriod(31556926);
}
#Bean
#Description("Thymeleaf template resolver serving HTML 5")
public ClassLoaderTemplateResolver templateResolver() {
var templateResolver = new ClassLoaderTemplateResolver();
templateResolver.setPrefix("templates/");
templateResolver.setCacheable(false);
templateResolver.setSuffix(".html");
templateResolver.setTemplateMode("HTML5");
templateResolver.setCharacterEncoding("UTF-8");
templateResolver.setOrder(0);
return templateResolver;
}
#Bean
#Description("Thymeleaf template engine with Spring integration")
public SpringTemplateEngine templateEngine() {
var templateEngine = new SpringTemplateEngine();
templateEngine.setTemplateResolver(templateResolver());
return templateEngine;
}
#Bean
#Description("Thymeleaf view resolver")
public ViewResolver viewResolver() {
var viewResolver = new ThymeleafViewResolver();
viewResolver.setTemplateEngine(templateEngine());
viewResolver.setCharacterEncoding("UTF-8");
return viewResolver;
}
}