Added some assertions about null icons.

client/texture/TaughtIcon.java

@@ -12,6 +12,10 @@ public class TaughtIcon implements IIcon
 	private IIcon p;
 
 	public TaughtIcon(IIcon o, float tightness) {
+		
+		if ( o == null )
+			throw new RuntimeException("Cannot create a wrapper icon with a null icon.");
+		
 		p = o;
 		this.tightness = tightness * 0.4f;
 	}