Better SkipBlock strategy (for benchmark felix-4960)

[seongjoonh]

We want to synthesize a patch that skips the entire if statement for the following code:

void someMethod() {
...
r = p.foo(); // NPE sink, where 'p' is the null pointer.
if (...) {
  r.xyz();
} else {
  for (...) {
     r.goo();
 }
return ...;