MDL-89075 theme_boost: fix anchored drawer height collapse

Anchored drawers are content-sized, but .drawercontent declared
flex: 1 1 0. A definite zero flex base gives the drawer nothing to
derive its height from, so it collapsed to the header.

Override flex-basis to auto in the anchored block so the behaviour no
longer depends on minification.

Author: muhammadarnaldo

public/theme/boost/scss/moodle/drawer.scss

@@ -324,6 +324,12 @@ $right-drawer-width: 320px;
                     padding-bottom: $drawer-anchored-header-bottom-gap;
                 }
             }
+
+            // The drawer is content-sized here, so the scrollable area must
+            // contribute its content height instead of a zero flex base.
+            .drawercontent {
+                flex-basis: auto;
+            }
         }
 
         .drawer.drawer-left {

public/theme/boost/style/moodle.css

@@ -34757,6 +34757,12 @@ body.drawer-ease {
     height: auto;
     padding-bottom: 0.5rem;
   }
+  .pagelayout-standard .drawer.drawer-left .drawercontent,
+  .pagelayout-standard .drawer.drawer-right .drawercontent,
+  body.limitedwidth .drawer.drawer-left .drawercontent,
+  body.limitedwidth .drawer.drawer-right .drawercontent {
+    flex-basis: auto;
+  }
   .pagelayout-standard .drawer.drawer-left,
   body.limitedwidth .drawer.drawer-left {
     left: auto;

public/theme/classic/style/moodle.css

@@ -32397,6 +32397,12 @@ body.drawer-ease {
     height: auto;
     padding-bottom: 0.5rem;
   }
+  .pagelayout-standard .drawer.drawer-left .drawercontent,
+  .pagelayout-standard .drawer.drawer-right .drawercontent,
+  body.limitedwidth .drawer.drawer-left .drawercontent,
+  body.limitedwidth .drawer.drawer-right .drawercontent {
+    flex-basis: auto;
+  }
   .pagelayout-standard .drawer.drawer-left,
   body.limitedwidth .drawer.drawer-left {
     left: auto;