[dotify] Handle break-before="page" after only empty blocks on current page

when some of those blocks have markers.

Author: bertfrees

libs/dotify/dotify.formatter.impl/src/org/daisy/dotify/formatter/impl/page/RowGroupDataSource.java

@@ -206,6 +206,7 @@ public RowGroupDataSource getDataSource() {
 	@Override
 	protected void newRowGroupSequence(BreakBefore breakBefore, VerticalSpacing vs) {
 		if (groups!=null) {
+			// this means ScenarioData.maybeNewRowGroupSequence() did not return true for this block
 			throw new IllegalStateException();
 		} else {
 			groups = new ArrayList<>();

libs/dotify/dotify.formatter.impl/src/org/daisy/dotify/formatter/impl/page/ScenarioData.java

@@ -43,16 +43,12 @@ float calcSize() {
 		return size;
 	}
 
-	private boolean isDataEmpty() {
-		return (dataGroups.isEmpty()||dataGroups.peek().getGroup().isEmpty());
-	}
-	
 	protected boolean hasSequence() {
 		return !dataGroups.isEmpty();
 	}
 
 	protected boolean hasResult() {
-		return !isDataEmpty();
+		return !dataGroups.isEmpty();
 	}
 
 	protected void newRowGroupSequence(BreakBefore breakBefore, VerticalSpacing vs) {