fix NPE when resizing to a very small width

Signed-off-by: Florian Thienel <florian@thienel.org>
diff --git a/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/boxes/InlineFrame.java b/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/boxes/InlineFrame.java
index 067db97..69f0e73 100644
--- a/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/boxes/InlineFrame.java
+++ b/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/boxes/InlineFrame.java
@@ -161,6 +161,8 @@
 	@Override
 	public void layout(final Graphics graphics) {
 		if (component == null) {
+			width = 0;
+			height = 0;
 			return;
 		}
 
diff --git a/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/boxes/RootBox.java b/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/boxes/RootBox.java
index 3d7ec69..24f9541 100644
--- a/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/boxes/RootBox.java
+++ b/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/boxes/RootBox.java
@@ -51,7 +51,7 @@
 	}
 
 	public void setWidth(final int width) {
-		this.width = width;
+		this.width = Math.max(0, width);
 	}
 
 	public int getHeight() {