Fix:the rounded corners of the folded file are not displayed correctly (#29953) (#30177)

Backport #29953 by @HEREYUA

Fix:    [#29933](#29933)

**Before**

![image](https://github.com/go-gitea/gitea/assets/37935145/71ec80f6-5896-4e4a-b686-4d792c11ebe2)

**After**

![image](https://github.com/go-gitea/gitea/assets/37935145/81348a61-946a-4562-881d-8d873e50228f)

Co-authored-by: HEREYUA <[email protected]>
Co-authored-by: silverwind <[email protected]>

Author: 3 people

web_src/css/modules/segment.css

@@ -69,7 +69,8 @@
   border-radius: 0 0 0.28571429rem 0.28571429rem;
 }
 
-.ui.segments:not(.horizontal) > .segment:only-child {
+.ui.segments:not(.horizontal) > .segment:only-child,
+.ui.segments:not(.horizontal) > .segment:has(~ .tw-hidden) { /* workaround issue with :last-child ignoring hidden elements */
   border-radius: 0.28571429rem;
 }