Better integrate elements into stock HA custom element support.

src/scss/elements.scss

@@ -1,4 +1,12 @@
 .element {
   position: absolute;
   transform: translate(-50%, -50%);
+}
+
+// Errors encountered by HA (not the card) during parsing of the configuration
+// (e.g. custom picture element that does not exist).
+hui-error-card.element {
+  inset: 0px;
+  background-color: var(--secondary-background-color, black);
+  transform: unset;
 }

src/scss/gallery.scss

@@ -3,6 +3,13 @@
 
 :host {
   overflow: auto;
+  -ms-overflow-style: none; /* Hide scrollbar: IE and Edge */
+  scrollbar-width: none;    /* Hide scrollbar: Firefox */
+}
+
+/* Hide scrollbar for Chrome, Safari and Opera */
+:host::-webkit-scrollbar {
+  display: none;
 }
 
 .frigate-card-gallery {