avoid dead code insertion during insertOnEdge

[benSepanski]

if originalPred does not fall through, but is not a gotoStmt, then dead code can be inserted. For example, if inserting on the edge (point_src, point_tgt) here:

    if [some condition] goto label1    // point_src
    throw exception                    // originalPred
label1:
    return                             // point_tgt

This can be generating using a function such as

class Example
{
    public void example(int x)
    {
        if(x == 0)
        {
            throw new IllegalArgumentException("x should not be zero!");
        }
        return;
    }
}