fix nullpointer exception for embeddings without text message

src/main/java/org/stegosuite/application/StegosuitePresenter.java

@@ -46,15 +46,14 @@ public class StegosuitePresenter implements EmbeddingDoneListener, ExtractingDon
 		return embedding;
 	}
 
-	public void embedNotifying(EmbeddingProgress progressListener, String message, String password) {
+	public void embedNotifying(EmbeddingProgress progressListener, String password) {
 		this.progressListener = progressListener;
 
-		embed(message, password);
+		embed(password);
 	}
 
-	public void embed(String message, String password) {
+	public void embed(String password) {
 		try {
-			addMessageToPayload(message);
 			setPassword(password);
 			embedData();
 		} catch (SteganoEmbedException e) {
@@ -62,7 +61,7 @@ public class StegosuitePresenter implements EmbeddingDoneListener, ExtractingDon
 		}
 	}
 
-	private void addMessageToPayload(String message) {
+	public void addMessageToPayload(String message) {
 		payload.addBlock(new MessageBlock(message));
 	}
 	

src/main/java/org/stegosuite/ui/cli/Cli.java

@@ -39,8 +39,12 @@ public class Cli
 			return;
 
 		pointFilter(cmd);
+		
 		String message = cmd.getOptionValue("m");
-
+		if (message != null) {
+			presenter.addMessageToPayload(message);
+		}
+		
 		String[] files = cmd.getOptionValues("f");
 		if (files != null) {
 			for (String string : files) {
@@ -50,11 +54,11 @@ public class Cli
 
 		String key = cmd.getOptionValue("k");
 
-		embed(message, key);
+		embed(key);
 	}
 
-	private void embed(String message, String key) {
-		presenter.embed(message, key);
+	private void embed(String key) {
+		presenter.embed(key);
 	}
 
 	public void extract(CommandLine cmd) {
@@ -121,7 +125,7 @@ public class Cli
 
 	@Override
 	public void showEmbeddingError(SteganoEmbedException e) {
-		e.printStackTrace();
+		LOG.info(e.getMessage());
 	}
 
 	@Override

src/main/java/org/stegosuite/ui/gui/EmbedUi.java

@@ -172,8 +172,10 @@ public class EmbedUi implements StegosuiteUI {
 
 		String message = messageField.getText();
 		String password = getEnteredPassword();
+		
+		presenter.addMessageToPayload(message);
 
-		runInNewThread(() -> presenter.embedNotifying(progress, message, password));
+		runInNewThread(() -> presenter.embedNotifying(progress, password));
 	}
 
 	private void startExtraction(Composite compositeControls) {

src/test/java/org/stegosuite/EmbeddingAndExtractingTest.java

@@ -84,7 +84,8 @@ public class EmbeddingAndExtractingTest {
     private void embedPayload(String imageName, String password, String message) throws SteganoImageException, SteganoEmbedException {
         String imagePath = pathOf(imageName);
         StegosuitePresenter presenter = getPresenterFor(imagePath);
-        presenter.embedNotifying(new EmbeddingProgress(), message, password);
+        presenter.addMessageToPayload(message);
+        presenter.embedNotifying(new EmbeddingProgress(), password);
     }
 
     private void extractPayload(String imagePath, String password) throws SteganoImageException, SteganoExtractException {

src/test/java/org/stegosuite/PresenterTest.java

@@ -64,7 +64,8 @@ public class PresenterTest implements StegosuiteUI, Observer {
 	@Test
 	public void embeddingTest() throws Exception {
 		presenter = presenterWithImage(IMAGE_NAME);
-		presenter.embedNotifying(progressListener, message, password);
+		presenter.addMessageToPayload(message);
+		presenter.embedNotifying(progressListener, password);
 
 		assertEquals(100, currentProgress);
 		assertNotNull(outputVisualizer);
@@ -76,7 +77,8 @@ public class PresenterTest implements StegosuiteUI, Observer {
 	@Test
 	public void extractTest() throws Exception {
 		presenter = presenterWithImage(IMAGE_NAME);
-		presenter.embedNotifying(progressListener, message, password);
+		presenter.addMessageToPayload(message);
+		presenter.embedNotifying(progressListener, password);
 		resetCurrentProgress();
 
 		presenter = presenterWithImage(EMBEDDED_IMAGE);
@@ -92,7 +94,8 @@ public class PresenterTest implements StegosuiteUI, Observer {
 	public void extractFileTest() throws Exception {
 		presenter = presenterWithImage(IMAGE_NAME);
 		presenter.addFileToPayload(pathOf(FILE_NAME));
-		presenter.embedNotifying(progressListener, message, password);
+		presenter.addMessageToPayload(message);
+		presenter.embedNotifying(progressListener, password);
 		resetCurrentProgress();
 		presenter = presenterWithImage(EMBEDDED_IMAGE);