Adwaita: add minimum size for marks

It's still suboptimal, because there's no way to control the size of the
indicator alone, but this does the job for now.

gtk/theme/Adwaita/_common.scss

@@ -2578,6 +2578,8 @@ scale {
   }
 
   marks { color: gtkalpha(currentColor, 0.4); }
+  &.horizontal marks { min-height: 8px; }
+  &.vertical marks { min-width: 8px; }
 
   // *WARNING* scale with marks madness following
 

gtk/theme/Adwaita/gtk-contained-dark.css

@@ -2757,6 +2757,10 @@ scale {
         -gtk-icon-shadow: none; }
   scale marks {
     color: alpha(currentColor,0.4); }
+  scale.horizontal marks {
+    min-height: 8px; }
+  scale.vertical marks {
+    min-width: 8px; }
   scale.color.horizontal trough > trough > slider, scale.horizontal contents:last-child:not(:only-child) > trough > slider {
     margin: -9px;
     border-style: none;

gtk/theme/Adwaita/gtk-contained.css

@@ -2788,6 +2788,10 @@ scale {
         -gtk-icon-shadow: none; }
   scale marks {
     color: alpha(currentColor,0.4); }
+  scale.horizontal marks {
+    min-height: 8px; }
+  scale.vertical marks {
+    min-width: 8px; }
   scale.color.horizontal trough > trough > slider, scale.horizontal contents:last-child:not(:only-child) > trough > slider {
     margin: -9px;
     border-style: none;