Fixed error when processing adjacent empty emphasises

Author: Torsten Krause

module/handler/text-commonmark/src/main/java/io/markdom/handler/text/commonmark/ContentBuffer.java

@@ -196,9 +196,11 @@ private void moveLineBreakInFrontOfBeginnings() {
 	}
 
 	private void unprepareLine() {
-		if (!pendingLineBreak) {
-			pendingLineBreak = true;
-			unbeginNewLine();
+		if (!isEmpty()) {
+			if (!pendingLineBreak) {
+				pendingLineBreak = true;
+				unbeginNewLine();
+			}
 		}
 	}
 

module/handler/text-commonmark/src/test/java/io/markdom/handler/commonmark/CommonmarkTextMarkdomHandlerContentTests.java

@@ -1798,6 +1798,24 @@ public void nestedEmphasisesWithoutConttentsInbetweenLinebreaksAreRemoved2() {
 
 	}
 
+	@Test
+	public void nestedEmphasisesWithoutAnyContentAreRemoved() {
+
+		// @formatter:off
+		paragraph.addContents(
+			factory.emphasisContent(
+				MarkdomEmphasisLevel.LEVEL_2,
+				factory.emphasisContent(
+					MarkdomEmphasisLevel.LEVEL_1
+				)
+			)
+		);
+		// @formatter:on
+
+		assertEquals("\\", getCommonmarkText());
+
+	}
+
 	@Test
 	public void adjacentEmphasisesAreRemovedSurroundedByMultipleStars() {
 
@@ -1890,6 +1908,24 @@ public void adjacentEmphasisesAreRemovedSurroundedByMultipleUnderscoresAndStars(
 
 	}
 
+	@Test
+	public void adjacentEmphasisesWithoutAnyContentAreRemoved() {
+
+		// @formatter:off
+		paragraph.addContents(
+			factory.emphasisContent(
+				MarkdomEmphasisLevel.LEVEL_2
+			),
+			factory.emphasisContent(
+				MarkdomEmphasisLevel.LEVEL_1
+			)
+		);
+		// @formatter:on
+
+		assertEquals("\\", getCommonmarkText());
+
+	}
+
 	@Test
 	public void singleEmphasisesCanBeInterruptedBySoftLineBreaks() {
 
@@ -3056,7 +3092,8 @@ public void singleTextContentThatContainsOnlyThreeOrMoreDashesWithOptionalSpaces
 
 	@ParameterizedTest
 	@ValueSource(strings = { "___", "__ __", "_ _ _", "__ __ __" })
-	public void singleTextContentThatContainsOnlyThreeOrMoreUnderscoredWithOptionalSpacesIsEscapedTheBeginning(String underscores) {
+	public void singleTextContentThatContainsOnlyThreeOrMoreUnderscoredWithOptionalSpacesIsEscapedTheBeginning(
+			String underscores) {
 
 		// @formatter:off
 		paragraph.addContents(