java.lang.String.isEmpty is only since 1.6

Change-Id: I43fd404e96192af3c0a8734c4547cee3b906c935

reportbuilder/java/org/libreoffice/report/SDBCReportDataFactory.java

@@ -258,7 +258,7 @@ public class SDBCReportDataFactory implements DataSourceFactory
                                 prefix = (String)column.getPropertyValue("TableName");
                                 if (prefix == null)
                                     prefix = "";
-                                if (!prefix.isEmpty())
+                                if (prefix.length() != 0)
                                 {
                                     prefix = quote + prefix + quote + ".";
                                 }