fix(loader): Add casting not support exception

Author: MuLeiSY2021

hugegraph-loader/src/main/java/org/apache/hugegraph/loader/util/DataTypeUtil.java

@@ -163,6 +163,11 @@ private static Object parseSingleValue(String key, Object rawValue,
                 FileSource fileSource = (FileSource) source;
                 dateFormat = fileSource.dateFormat();
                 timeZone = fileSource.timeZone();
+            } else {
+                throw new IllegalArgumentException(
+                        "Date format source " +
+                        source.getClass().getName() +
+                        " not supported");
             }
 
             if (extraDateFormats == null || extraDateFormats.isEmpty()) {