Attempt to merge arguments from views without any arguments

I'm getting a php error as shown below:

warning: array_merge() [function.array-merge]: Argument #2 is not an array in modules/contrib-head/views_union/views_union.module on line 225.

I think that this is caused because I'm merging two views that don't use arguments. But I haven't really dived into the code to know for sure.

The attached simple patch checks for this, and doesn't do the array merge, when the $args is empty.