Some large explainxkcd entries don't send when being split into fields

[Hpmason]

Some explainxkcd's are too long and are split into multiple fields.

Examples:

• ExplainXKCD 2431 4,049 characters

Steps to take:
The code that splits the explanation into fields is likely creating fields that are longer than the 1024 limit, which only causes certain comics to be affected.
Debug embed.rs and it's output to determine what causes the oversized fields.