Fix styles of error pages (#5335)

Signed-off-by: Lynx Kotoura <admin@sanin.link>

Signed-off-by: Lynx Kotoura <admin@sanin.link>

app/javascript/styles/basics.scss

@@ -29,8 +29,7 @@ body {
     font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", "Oxygen", "Ubuntu", "Cantarell", "Fira Sans", "Droid Sans", "Helvetica Neue", mastodon-font-sans-serif, sans-serif;
   }
 
-  &.app-body,
-  &.error {
+  &.app-body {
     position: fixed;
     width: 100%;
     height: 100%;
@@ -70,14 +69,22 @@ body {
   }
 
   &.error {
+    position: absolute;
     text-align: center;
     color: $ui-primary-color;
-    padding: 20px;
+    background: $ui-base-color;
+    width: 100%;
+    height: 100%;
+    padding: 0;
     display: flex;
     justify-content: center;
     align-items: center;
 
-    .dialog img {
+    .dialog {
+      vertical-align: middle;
+      margin: 20px;
+
+      img {
         display: block;
         max-width: 470px;
         width: 100%;
@@ -85,12 +92,13 @@ body {
         margin-top: -120px;
       }
 
-    .dialog h1 {
+      h1 {
         font-size: 20px;
         line-height: 28px;
         font-weight: 400;
       }
     }
+  }
 }
 
 button {