Throw exception when clone repository name is blank

Prevents corrupting the shared drive by writing directly into the
root worktree or gitdir paths when the name cannot be derived.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/main/java/be/seeseepuff/webgit/service/GitService.java

@@ -36,6 +36,8 @@ public class GitService
 	{
 		if (name == null || name.isBlank())
 			name = deriveRepositoryName(url);
+		if (name.isBlank())
+			throw new IllegalArgumentException("Repository name must not be blank");
 		Path worktree = properties.getWorktreePath().resolve(name);
 		Path gitDir = properties.getGitDirPath().resolve(name);