Fix assigning user to pull request without labels

Fixes #1057

commands/pull_request.go

@@ -223,10 +223,17 @@ func pullRequest(cmd *Command, args *Args) {
 		if flagPullRequestAssignee != "" || flagPullRequestMilestone > 0 ||
 			flagPullRequestLabels != "" {
 
+			labels := []string{}
+			for _, label := range strings.Split(flagPullRequestLabels, ",") {
+				if label != "" {
+					labels = append(labels, label)
+				}
+			}
+
 			params := octokit.IssueParams{
 				Assignee:  flagPullRequestAssignee,
 				Milestone: flagPullRequestMilestone,
-				Labels:    strings.Split(flagPullRequestLabels, ","),
+				Labels:    labels,
 			}
 
 			err = client.UpdateIssue(baseProject, pr.Number, params)

features/pull_request.feature

@@ -605,7 +605,7 @@ Feature: hub pull-request
         json :html_url => "the://url", :number => 1234
       }
       patch('/repos/mislav/coral/issues/1234') {
-        assert :assignee => "mislav"
+        assert :assignee => "mislav", :labels => nil
         json :html_url => "the://url"
       }
       """