caret in PlaceholderBox should use full box height

Signed-off-by: Florian Thienel <florian@thienel.org>
diff --git a/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/layout/PlaceholderBox.java b/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/layout/PlaceholderBox.java
index dc10d9a..7561ee3 100644
--- a/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/layout/PlaceholderBox.java
+++ b/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/layout/PlaceholderBox.java
@@ -81,7 +81,7 @@
 	 */
 	@Override
 	public Caret getCaret(final LayoutContext context, final int offset) {
-		return new TextCaret(0, textTop, baseline - textTop);
+		return new TextCaret(0, 0, getHeight());
 	}
 
 	/**