Fix #1282 NullPointerException from Cocoon with invalid caterpillar

gradle.properties

@@ -1,9 +1,9 @@
 mcversion=1.9.4
-forgeversion=12.17.0.1944
+forgeversion=12.17.0.1948
 mcp_mappings=snapshot_20160525
 
 jei_version=3.4.0.+
 
 version_major=5
 version_minor=0
-version_patch=5
+version_patch=6

src/main/java/forestry/lepidopterology/tiles/TileCocoon.java

@@ -191,6 +191,11 @@ public class TileCocoon extends TileEntity implements IStreamable, IOwnable, IBu
 	}
 	
 	public void onBlockTick() {
+		if (caterpillar == null) {
+			worldObj.setBlockToAir(getPos());
+			return;
+		}
+
 		maturationTime++;
 
 		IButterflyGenome caterpillarGenome = caterpillar.getGenome();