DBG_ASSERT -> assert

The only caller of GetResourceSkipHeader (BitmapEx ctor in
vcl/source/gdi/bitmapex.cxx) unconditionally expects *ppResMgr to be non-null
after the call.

Change-Id: I17e71df81019de5b78c4356c7aec967c50a5a6ae

tools/source/rc/resmgr.cxx

@@ -1075,15 +1075,11 @@ void * ResMgr::GetResourceSkipHeader( const ResId& rResId, ResMgr ** ppResMgr )
 {
     osl::Guard<osl::Mutex> aGuard( getResMgrMutex() );
 
-    DBG_ASSERT( rResId.GetResMgr(), "illegal ResId without ResMgr" );
     *ppResMgr = rResId.GetResMgr();
-    if( *ppResMgr )
-    {
-        (*ppResMgr)->GetResource( rResId );
-        (*ppResMgr)->Increment( sizeof( RSHEADER_TYPE ) );
-        return (*ppResMgr)->GetClass();
-    }
-    return getEmptyBuffer();
+    assert(*ppResMgr != nullptr);
+    (*ppResMgr)->GetResource( rResId );
+    (*ppResMgr)->Increment( sizeof( RSHEADER_TYPE ) );
+    return (*ppResMgr)->GetClass();
 }
 
 void ResMgr::PopContext( const Resource* pResObj )