Bug 1418438 - Avoid null deref in nsIDocShell's forcedCharset. r=emk

MozReview-Commit-ID: KsTWmlAhDp8

--HG--
extra : rebase_source : 21e7476103c03488628f72aa517031135cfa4fe7

docshell/base/nsDocShell.cpp

@@ -2187,7 +2187,11 @@ nsDocShell::SetForcedCharset(const nsACString& aCharset)
 NS_IMETHODIMP
 nsDocShell::GetForcedCharset(nsACString& aResult)
 {
-  mForcedCharset->Name(aResult);
+  if (mForcedCharset) {
+    mForcedCharset->Name(aResult);
+  } else {
+    aResult.Truncate();
+  }
   return NS_OK;
 }