Make certain members of the Issue type into Maybes

Author: John Wiegley

Github/Data/Definitions.hs

@@ -178,7 +178,7 @@ data GitObject = GitObject {
 data Issue = Issue {
  issueClosedAt :: Maybe GithubDate
  ,issueUpdatedAt :: GithubDate
- ,issueHtmlUrl :: String
+ ,issueHtmlUrl :: Maybe String
  ,issueClosedBy :: Maybe GithubOwner
  ,issueLabels :: [IssueLabel]
  ,issueNumber :: Int
@@ -188,7 +188,7 @@ data Issue = Issue {
  ,issuePullRequest :: PullRequestReference
  ,issueUrl :: String
  ,issueCreatedAt :: GithubDate
- ,issueBody :: String
+ ,issueBody :: Maybe String
  ,issueState :: String
  ,issueId :: Int
  ,issueComments :: Int