修复导出启动器时未正确从 .hmcl/background 中查找壁纸的问题 (#3936)

Author: Glavo

HMCL/src/main/java/org/jackhuang/hmcl/ui/export/ExportWizardProvider.java

@@ -127,7 +127,7 @@ public void execute() throws Exception {
                     zip.putTextFile(exported.toJson(), ".hmcl/hmcl.json");
                     zip.putFile(tempModpack, "modpack.zip");
 
-                    Path bg = Metadata.HMCL_CURRENT_DIRECTORY.resolve("bg");
+                    Path bg = Metadata.HMCL_CURRENT_DIRECTORY.resolve("background");
                     if (!Files.isDirectory(bg))
                         bg = Metadata.CURRENT_DIRECTORY.resolve("bg");
                     if (Files.isDirectory(bg))