added test-if-null for second default block in double-infix blocks

src/main/java/edu/mit/blocks/codeblocks/InfixBlockShape.java

@@ -117,8 +117,9 @@ public class InfixBlockShape extends BlockShape {
                     //TODO: check why RBlock on second connector is always NULL???
                     RenderableBlock connectedRBlock = rb.getWorkspace().getEnv().getRenderableBlock(curSocket.getBlockID());
 
+                    if(connectedRBlock != null) {//added for second default block in double-infix block letsgoING
 	                    //calculate and update the new socket point
-                    //update the socket point of this cursocket which should now adopt the plug socket point of its
+	                    //update the socket point of this which should now adopt the plug socket point of its
 	                    //connected block since we're also adopting the left side of its shape
 	
 	                    //Use coordinates when the zoom level is 1.0 to calculate socket point
@@ -154,8 +155,7 @@ public class InfixBlockShape extends BlockShape {
 	                        maxX = (float) gpBottom.getCurrentPoint().getX();
 	                    }
 	                    gpBottom.lineTo(maxX, (float) gpBottom.getCurrentPoint().getY());
-
-
+	                    }
                 }