Mac: Fix crash while dragging a tab alone in a window.

chrome/browser/cocoa/tab_strip_controller.mm

Index: chrome/browser/cocoa/tab_strip_controller.mm
diff --git a/chrome/browser/cocoa/tab_strip_controller.mm b/chrome/browser/cocoa/tab_strip_controller.mm
index f431c93997b3f40c9f094052d1bb977aee30121d..4720d5f4efb855848a38fa64ee884967ff7bc43f 100644
--- a/chrome/browser/cocoa/tab_strip_controller.mm
+++ b/chrome/browser/cocoa/tab_strip_controller.mm
@@ -631,6 +631,12 @@ static const float kIndentLeavingSpaceForControls = 64.0;
   NSView* tab = [self viewAtIndex:index];
   [tab removeFromSuperview];
 
+  // Clear the tab controller's target.
+  // TODO(viettrungluu): [crbug.com/23829] Find a better way to handle the tab
+  // controller's target.
+  TabController* tabController = [tabArray_ objectAtIndex:index];
+  [tabController setTarget:nil];
+
   if ([hoveredTab_ isEqual:tab]) {
     hoveredTab_ = nil;
   }