RFR: 1984: SKARA bot couldn't handle jep command if the jep doesn't have JEP Number [v2]

[Zhao Song]

> A user issued command /jep JDK-8310626 in https://github.com/openjdk/jdk/pull/15103 and skara bot kept throwing exceptions because the JEP doesn't have a JEP number. 
> 
> @kevinrushforth suggested that it makes more sense to make skara bot be able to associate a PR with a JEP before it is a Candidate.

Zhao Song has updated the pull request incrementally with one additional commit since the last revision:

  update

-------------

Changes:
  - all: https://git.openjdk.org/skara/pull/1541/files
  - new: https://git.openjdk.org/skara/pull/1541/files/d9e1ccbd..2d73a3d7

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=skara&pr=1541&range=01
 - incr: https://webrevs.openjdk.org/?repo=skara&pr=1541&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/skara/pull/1541.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1541/head:pull/1541

PR: https://git.openjdk.org/skara/pull/1541