BIT-1280: Fix checking vector indices via "in".

$ cat test.bro
local vec: vector of string = { "zero" };
vec[2] = "two";
print 0 in vec, 1 in vec, 2 in vec;

$ bro -b test.bro
T, F, T
Fix segfault if when statement's RHS is unitialized.

If it is ever assigned a value, the body of the when can be triggered as
usual.

Addresses BIT-1176.
Merge remote-tracking branch 'origin/topic/jsiwek/bit-1280'

* origin/topic/jsiwek/bit-1280:
  BIT-1280: Fix checking vector indices via "in".

BIT-1280 #merged.
Merge remote-tracking branch 'origin/topic/jsiwek/bit-1176'

* origin/topic/jsiwek/bit-1176:
  Fix segfault if when statement's RHS is unitialized.

BIT-1176 #merged
Adding call to new binpac::init() function.
Updating submodule(s).

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Updating submodule(s).

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