Handle missing default branch better in owner/repo/branches page#18290

wxiaoguang merged 5 commits intogo-gitea:maingo-gitea/gitea:mainfrom

zeripath:fix-18265-prevent-ISE-if-no-default-branchzeripath/gitea:fix-18265-prevent-ISE-if-no-default-branchCopy head branch name to clipboard