A fix to bug 43351.

A softer landing on a failed initialization.  It checks for a null
before deallocating.  This does not affect the success path.

This was a patch, and I reviewed it:  (r=rayw)

xpcom/components/nsNativeComponentLoader.cpp

@@ -983,7 +983,9 @@ nsNativeComponentLoader::UnloadAll(PRInt32 aWhen)
     callData.when = aWhen;
 
     // Cycle through the dlls checking to see if they want to be unloaded
+    if (mDllStore) {
         mDllStore->Enumerate(nsFreeLibraryEnum, &callData);
+    }
     return NS_OK;
 }