fix(libreoffice): keep original extension all the time for preserved filenames in zipped output

pkg/modules/api/context_test.go

@@ -190,11 +190,15 @@ func TestContext_GeneratePath(t *testing.T) {
 		dirPath: "/foo",
 	}
 
-	path := ctx.GeneratePath(".pdf")
-
+	path := ctx.GeneratePath("", ".pdf")
 	if !strings.HasPrefix(path, ctx.dirPath) {
 		t.Errorf("expected '%s' to start with '%s'", path, ctx.dirPath)
 	}
+
+	path = ctx.GeneratePath("foo.txt", ".pdf")
+	if !strings.Contains(path, "foo.txt.pdf") {
+		t.Errorf("expected '%s' to start with '%s'", path, ctx.dirPath)
+	}
 }
 
 func TestContext_AddOutputPaths(t *testing.T) {