refactor: fixes found from internal tests

Author: andrewseguin

src/material/core/tokens/_m2-utils.scss

@@ -1,4 +1,5 @@
 @use 'sass:map';
+@use './m2';
 
 // Gets the theme's system values as a flat map.
 @function get-system($theme) {
@@ -7,5 +8,10 @@
     @return $system;
   }
 
+  // If the $theme is a typography-config, convert it to a system map.
+  @if map.has-key($theme, body-1) {
+    @return m2.md-sys-typescale-values($theme);
+  }
+
   @return ();
 }

src/material/list/_list-theme.scss

@@ -156,7 +156,7 @@
     // TODO(mmalerba): Discuss with MDC about adding them, or create custom tokens.
     .mdc-list-group__subheader {
       $system: m2-utils.get-system($theme);
-      font: map.get($system, label-large, font);
+      font: map.get($system, label-large);
       letter-spacing: map.get($system, label-large-tracking);
     }
   }