Null Handling for EventType Supplier

Applicable to the Log4JLoggerFactory (SPI), in order for the API to remain
consistent the implementation needs to allow for null EventType
references.

Author: jeremiahjstacey

src/main/java/org/owasp/esapi/logging/appender/EventTypeLogSupplier.java

@@ -39,6 +39,6 @@ public EventTypeLogSupplier(EventType evtyp) {
 
 	@Override
 	public String get() {
-		return eventType.toString();
+		return eventType == null ? "" : eventType.toString();
 	}
 }

src/test/java/org/owasp/esapi/logging/appender/EventTypeLogSupplierTest.java

@@ -15,4 +15,12 @@ public void testEventTypeLog() {
 
 		assertEquals(eventType.toString(), supplier.get());
 	}
+	
+	@Test
+	public void testNullEventTypeLog() {
+		
+		EventTypeLogSupplier supplier = new EventTypeLogSupplier(null);
+		
+		assertEquals("", supplier.get());
+	}
 }