Fixing bug 198254. Fix crash when closing javascript created window. r+sr=bzbarsky@mit.edu

layout/base/nsPresShell.cpp

@@ -1928,6 +1928,9 @@ PresShell::Destroy()
   // pres shell to NULL
   if (mPresContext) {
     mPresContext->SetShell(nsnull);
+
+    // Clear the link handler (weak reference) as well
+    mPresContext->SetLinkHandler(nsnull);
   }
 
   if (mViewEventListener) {

layout/html/base/src/nsPresShell.cpp

@@ -1928,6 +1928,9 @@ PresShell::Destroy()
   // pres shell to NULL
   if (mPresContext) {
     mPresContext->SetShell(nsnull);
+
+    // Clear the link handler (weak reference) as well
+    mPresContext->SetLinkHandler(nsnull);
   }
 
   if (mViewEventListener) {