Merge pull request 'Fix problem of PL #956' (#963) from mskf1383/Plume:main into main

Reviewed-on: https://git.joinplu.me/Plume/Plume/pulls/963
Reviewed-by: KitaitiMakoto <kitaitimakoto@noreply@joinplu.me>

assets/themes/default/_global.scss

@@ -230,6 +230,10 @@ p.error {
     }
   }
   
+   header {
+    display: flex;
+  }
+
   h3 {
     flex-grow: 1;
     margin: 0;
@@ -237,7 +241,7 @@ p.error {
     font-size: 1.75em;
     font-weight: normal;
     line-height: 1.10;
-    display: block;
+    display: inline-block;
     position: relative;
     a {
       display: block;