Avoid a very rare case, where we might get an "IllegalArgumentException" from "Lists.partition()", in case the "sizeOfUrlReports" is <= 3.

src/main/java/eu/openaire/urls_controller/util/ParquetFileUtils.java

@@ -192,6 +192,8 @@ public class ParquetFileUtils {
                 // In case the above method returns an error, nothing happens. We just have only the initial payloads to insert to the DB.
 
                 int sizeOfEachSubList = (int)(sizeOfUrlReports * 0.33);  // We want 3 sub-lists for the payloads.
+                if ( sizeOfEachSubList == 0 )   // If the "sizeOfUrlReports" is <= 3.
+                    sizeOfEachSubList = 1;
                 // There may be 1 more with very few elements, due to non-persisted splitting. Unfortunately, we cannot st the number of splits, only the size of most splits.
                 if ( sizeOfEachSubList > 10 ) {
                     List<List<UrlReport>> finalSubLists = Lists.partition(urlReports, sizeOfEachSubList);  // This needs the "sizeOfEachSubList" to be above < 0 >.