Apply suggestions from code review

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: tfmorris

src/main/java/org/openrefine/extensions/commons/importer/FileFetcher.java

@@ -79,7 +79,7 @@ private JsonNode getJson(HttpUrl url) throws IOException {
                 if (response.body() != null) {
                     return new ObjectMapper().readTree(response.body().string());
                 } else  {
-                    return new ObjectMapper().readTree("[]");
+                    return new ObjectMapper().readTree("{}");
                 }
             } else {
                 throw new IOException("API request failed with status code: " + response.code() + ", body: " + response.message());
@@ -179,8 +179,7 @@ public JsonNode next() {
             try {
                 getContinuationResults(urlContinue);
             } catch (IOException e) {
-                // TODO Auto-generated catch block
-                e.printStackTrace();
+                throw new UncheckedIOException("Failed to fetch continuation results for category: " + categoryName, e);
             }
             indexRow = 0;
         }