Fails to serialize when entire vector contents are erased

[julianharbarth]

See the two added tests. The first one passes as expected. The second one fails.

Might be related, but I don't think neither of the two erase functions in basic_vector ensure that

cista/include/cista/serialization.h

Line 657 in eb1b019

c.require((el->size() == 0) == (el->el_ == nullptr), "vec size=0 <=> ptr=0");

or similar are satisfied.

[felixguendling]

Thanks! I think #109 should fix the problem.

For in-memory vectors the condition does not apply. However, the require you mentioned is only checked for serialized vectors where the condition is always true.