Fix scroll bug on firefox

_sass/modules/_layout.scss

@@ -1,4 +1,3 @@
-
 $sidebar-width: 250px;
 $logo-height: 130px;
 $wrapper-width: 800px;
@@ -95,34 +94,16 @@ body {
 }
 
 .sidebar__nav {
-  padding: $spacing-unit $spacing-unit ($spacing-unit + $logo-height); // Add a bit more padding at the bottom for consistency.
+
   font-weight: bold;
   max-height: 100%;
-  overflow-y: scroll;
-
-  li {
-    list-style: none;
-
-    a {
-      color: $color-white;
-
-      &:hover {
-        text-decoration: none;
-      }
-    }
-  }
+  overflow-y: auto;
 }
 
-.section {
-  margin: 0px;
-
-  > li {
-    margin-bottom: $spacing-unit / 2;
-
-    &:last-child {
-      margin-bottom: $spacing-unit;
-    }
-  }
+.sidebar__nav-interior {
+  height: 100%;
+  // Add a bit more padding at the bottom for consistency.
+  padding: $spacing-unit $spacing-unit ($spacing-unit + $logo-height);
 }
 
 .section__header {
@@ -131,13 +112,22 @@ body {
   color: $color-white;
   margin-top: 0;
   margin-bottom: $spacing-unit / 4;
+
+  .section__links + & {
+    margin-top: $spacing-unit;
+  }
 }
 
 .section__links {
-  margin-left: $spacing-unit / 2;
-  margin-bottom: $spacing-unit;
-  font-weight: normal;
   font-size: 0.9em;
+  font-weight: normal;
+
+  list-style: none;
+  margin-left: $spacing-unit / 2;
+}
+
+.section__item {
+  list-style: none;
 }
 
 .section__link {
@@ -145,13 +135,26 @@ body {
   margin-top: $spacing-unit/4;
   opacity: 0.75;
   text-decoration: none;
+  color: $color-white;
 
   &:hover {
     opacity: 1;
+    text-decoration: none;
+  }
+
+  &:empty {
+    // there is an error in the liquid logic that spits out a
+    // empty last-child
+    display: none;
+  }
+
+  &:visited {
+    color: $color-white;
   }
 }
 
 .section__link--is-active {
   font-weight: bold;
   opacity: 1;
+  color: $color-white;
 }