Disallow empty titles (#5785)

* add util method and tests

* make sure the title of an issue cannot be empty

* wiki title cannot be empty

* pull request title cannot be empty

* update to make use of the new util methof

routers/repo/issue.go

@@ -355,7 +355,7 @@ func setTemplateIfExists(ctx *context.Context, ctxDataKey string, possibleFiles
 	}
 }
 
-// NewIssue render createing issue page
+// NewIssue render creating issue page
 func NewIssue(ctx *context.Context) {
 	ctx.Data["Title"] = ctx.Tr("repo.issues.new")
 	ctx.Data["PageIsIssueList"] = true
@@ -494,6 +494,11 @@ func NewIssuePost(ctx *context.Context, form auth.CreateIssueForm) {
 		return
 	}
 
+	if util.IsEmptyString(form.Title) {
+		ctx.RenderWithErr(ctx.Tr("repo.issues.new.title_empty"), tplIssueNew, form)
+		return
+	}
+
 	issue := &models.Issue{
 		RepoID:      repo.ID,
 		Title:       form.Title,