style: fix block border

src/main/frontend/components/block.css

@@ -87,7 +87,15 @@
 .ls-block {
   min-height: 24px;
   padding: 2px 0;
-  border-bottom: 1px solid var(--ls-primary-background-color);
+  border-bottom: 1px solid transparent;
+
+  &.selected {
+    border-bottom-color: var(--ls-primary-background-color);
+
+    &:last-child {
+      border-bottom-color: transparent;
+    }
+  }
 
   img {
     box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);