Check setDelimiter() for empty string

Signed-off-by: Mykola Faryma <m.faryma@partner.samsung.com>

src/main/java/org/apache/commons/csv/CSVFormat.java

@@ -346,6 +346,9 @@ public final class CSVFormat implements Serializable {
             if (containsLineBreak(delimiter)) {
                 throw new IllegalArgumentException("The delimiter cannot be a line break");
             }
+            if (delimiter.isEmpty()) {
+                throw new IllegalArgumentException("The delimiter cannot be empty");
+            }
             this.delimiter = delimiter;
             return this;
         }

src/test/java/org/apache/commons/csv/CSVFormatTest.java

@@ -1569,4 +1569,9 @@ public class CSVFormatTest {
         final CSVFormat formatWithRecordSeparator = CSVFormat.DEFAULT.withSystemRecordSeparator();
         assertEquals(System.lineSeparator(), formatWithRecordSeparator.getRecordSeparator());
     }
+
+    @Test
+    public void testDelimiterEmptyStringThrowsException1() {
+        assertThrows(IllegalArgumentException.class, () -> CSVFormat.DEFAULT.builder().setDelimiter("").build());
+    }
 }