Uncaught exception when trying to remove pagination of deleted message

[SebastiaanZ]

When a message with pagination is removed before the bot tries to remove the pagination reactions, an exception will be raised and displayed in channel:

To reproduce this, issue the !tags command and remove the message before the bot removes the pagination.

Although this will be a rare event, since it needs moderator removal, we probably want to suppress it anyway so it doesn't show up like above in public channels.

[kraktus]

I think this issue is fixed, or at least I did achieve to reproduce it, either by using !helps or !tags commands.

[scragly]

I've verified just now that the bug is still present.

[MarkKoz]

Duplicate of #770 and fixed in #771.