[M96][Extensions] Drag/drop pinned extensions only when extension exists

An extension can be deleted while dragging. Now, dropping will only
happen if there is an action for the extension dragged (either if the
drag was inside or outside the container).

Screencast:
https://screencast.googleplex.com/cast/NTI4ODA4NjgxMzU0MDM1MnwzNzU0MjBjNS0zMQ

Bug: 1266510

(cherry picked from commit 92cf863b4197ec51ed3d0be9aa9abd33a78165c7)

Change-Id: Ib7ed338ac792d455143008d81cbb0552092cec51
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3263281
Reviewed-by: Caroline Rising <corising@chromium.org>
Commit-Queue: Emilia Paz <emiliapaz@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#939447}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3307077
Reviewed-by: Devlin Cronin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/branch-heads/4664@{#1201}
Cr-Branched-From: 24dc4ee75e01a29d390d43c9c264372a169273a7-refs/heads/main@{#929512}

diff --git a/chrome/browser/ui/views/extensions/extensions_toolbar_container.cc b/chrome/browser/ui/views/extensions/extensions_toolbar_container.cc
index 1afa725..b881c00 100644
--- a/chrome/browser/ui/views/extensions/extensions_toolbar_container.cc
+++ b/chrome/browser/ui/views/extensions/extensions_toolbar_container.cc

@@ -640,6 +640,12 @@
   BrowserActionDragData data;
   if (!data.Read(event.data()))
     return ui::DragDropTypes::DRAG_NONE;
+
+  // Check if there is an extension for the dragged icon (e.g. an extension can
+  // be de deleted while dragging its icon).
+  if (!GetActionForId(data.id()))
+    return ui::DragDropTypes::DRAG_NONE;
+
   size_t before_icon = 0;
   // Figure out where to display the icon during dragging transition.
 
@@ -670,6 +676,9 @@
 }
 
 void ExtensionsToolbarContainer::OnDragExited() {
+  if (!drop_info_)
+    return;
+
   const ToolbarActionsModel::ActionId dragged_extension_id =
       drop_info_->action_id;
   drop_info_.reset();
@@ -744,6 +753,9 @@
                            return GetViewForId(action_id) == GetViewForId(id);
                          });
   ToolbarActionView* extension_view = GetViewForId(*it);
+  if (!extension_view)
+    return;
+
   extension_view->SetImageModel(
       views::Button::STATE_NORMAL,
       visible ? ui::ImageModel::FromImageSkia(GetExtensionIcon(extension_view))