Add a redirect to the course enroll page for labs

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src/main/java/nl/tudelft/ewi/queue/controller/LabController.java

@@ -507,7 +507,7 @@ public class LabController {
 	/**
 	 * Processes a GET request asking for the CSV file representing the list of requests from the current lab.
 	 * This CSV file is created and sent to the requestor through a ResponseEntity.
-	 *
+	 * <p>
 	 * Headers are added to the response entity to indicate that the attached resource should be downloaded
 	 * and the user should not be redirected to a new page. Additionally, we indicate a name for the file.
 	 * https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Disposition
@@ -546,12 +546,14 @@ public class LabController {
 	@ExceptionHandler(AccessDeniedException.class)
 	public String notInLab(@AuthenticatedUser User user, HttpServletRequest request,
 			Exception e) {
-		Pattern testPattern = Pattern.compile("/lab/([0-9]+)/*");
+		Pattern testPattern = Pattern.compile("/lab/([0-9]+)[/]?.*");
 		Matcher matcher = testPattern.matcher(request.getRequestURI());
+
 		if (matcher.matches() && matcher.groupCount() == 1) {
-			Course course = labRepository.findById(Long.parseLong(matcher.group(1))).orElseThrow()
-					.getCourse();
-			return "redirect:/course/" + course.getId() + "/enroll";
+			Long labId = Long.parseLong(matcher.group(1));
+			return labRepository.findById(labId)
+					.map(lab -> "redirect:/course/" + lab.getCourse().getId() + "/enroll")
+					.orElse("redirect:/error/404");
 		}
 
 		logger.error("Access Denied: (User: {}, page: {})", user.getDisplayName(), request.getRequestURI());