Remove bad assert

Seems this assert was typoed, and was accidentally asserting the
nullness of something which is definitely not null.  This was causing
a number of false negatives when the tests were run with assertions
enabled.

Note that this commit completely removes the null checking since it
can't do any good: this code would NPE earlier if line was null.
Untag a batch of passing tests

These were failing on CI due to a bad assert.  Untag them now that the
offending assert is gone.  Note: there my be other tests which are
also clean now that the assert is gone.  Will check for them soon.
Merge pull request #760 from dmarcotte/bad-assert

Remove a bad assert and untag some tests it was affecting
binwrite should pass write only when options are not empty but don't have a "mode"
IO.sysopen accepts mode & permission that are nil
Merge pull request #763 from josedonizetti/io_binwrite

binwrite should pass write only when options are not empty but don't have a "mode"
add support for options and not truncating offset for IO.write
Merge pull request #766 from josedonizetti/sysopen_accepts_mode_and_permission_nil

IO.sysopen accepts mode & permission that are nil
Merge pull request #764 from josedonizetti/io_write

add support for options and not truncating offset for IO.write
raise ArgumentError when IO.new/IO.open last argument is not a hash or nil
Merge pull request #768 from josedonizetti/io_new_wrong_last_argument

raise ArgumentError when IO.new/IO.open last argument is not a hash or nil
Started with specs for adding edge to vertex
Added some more specs
Fixed the failing specs