R1:cfb5de6fa77f

Distinguish more carefully between "null" inline offsets and "0" inline offsets

Summary:
Ref T13513. Currently, when creating an inline by selecting a line range, slightly careless handling leads to an inline with "0" offsets (by passing "undefined" to the server). This causes the block to highlight every line except the last one as fully bright, which is incorrect.

An inline with "0" offsets and an inline with no offsets are different. Be more careful about passing offsets around and rendering them.