Make sure we've tried to create our CSSLoader before we try to dereference it.

Bug 289765, r+sr=jst, a=asa

content/base/src/nsDocument.cpp

@@ -1221,7 +1221,14 @@ nsDocument::SetHeaderData(nsIAtom* aHeaderField, const nsAString& aData)
     nsAutoString title;
     PRInt32 index;
 
-    mCSSLoader->SetPreferredSheet(aData);
+    // We lazily create our CSSLoader.
+    // XXXbz why?  Wouldn't it make more sense to just create it at
+    // document creation and not do all these null-checks all over?
+    nsICSSLoader* cssLoader = GetCSSLoader();
+    if (!cssLoader) {
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+    cssLoader->SetPreferredSheet(aData);
 
     PRInt32 count = mStyleSheets.Count();
     for (index = 0; index < count; index++) {

content/html/document/src/nsHTMLDocument.cpp

@@ -673,6 +673,10 @@ nsHTMLDocument::StartDocumentLoad(const char* aCommand,
   nsCAutoString contentType;
   aChannel->GetContentType(contentType);
 
+  // Note: we MUST set the compat mode and default namespace ID before we call
+  // StartDocumentLoad on our superclass (since that could force creation of a
+  // CSSLoader and the CSSLoader creation needs to know our compat mode and
+  // case sensitivity.
   if (contentType.Equals("application/xhtml+xml") &&
       (!aCommand || nsCRT::strcmp(aCommand, "view-source") != 0)) {
     // We're parsing XHTML as XML, remember that.