Remove useless concept of headless drawer and fix issue with drawer observer

packages/bbui/src/Drawer/Drawer.svelte

@@ -44,7 +44,7 @@
     if (get(openDrawers).length) {
       return
     }
-    observer.disconnect()
+    observer?.disconnect()
     observer = null
   }
 </script>
@@ -57,7 +57,6 @@
   import { fade } from "svelte/transition"
 
   export let title
-  export let headless = false
 
   const dispatch = createEventDispatcher()
   const spacing = 11
@@ -156,13 +155,11 @@
     {/if}
     <div
       class="drawer"
-      class:headless
       class:stacked={depth > 0}
       class:modal={$modal}
       transition:slide|local
       {style}
     >
-      {#if !headless}
       <header>
         <div class="text">{title}</div>
         <div class="buttons">
@@ -170,7 +167,6 @@
           <slot name="buttons" />
         </div>
       </header>
-      {/if}
       <slot name="body" />
       {#if !$modal && depth > 0}
         <div class="overlay" transition:fade|local={{ duration: 260 }} />

packages/builder/src/components/common/bindings/DrawerBindableSlot.svelte

@@ -175,11 +175,7 @@
   bind:this={bindingDrawer}
   {title}
   left={drawerLeft}
-  headless
 >
-  <svelte:fragment slot="description">
-    Add the objects on the left to enrich your text.
-  </svelte:fragment>
   <Button cta slot="buttons" disabled={!valid} on:click={saveBinding}>
     Save
   </Button>