PVS-Studio warning V588 for libxml

static int
xmlXPathCompOpEvalFirst(....)
{
  ...
  total += xmlXPathCompOpEvalFirst(....);
  ...
  total =+ xmlXPathCompOpEvalFilterFirst(ctxt, op, first);
  ...
}

This suspicious code was found in libxml project by PVS-Studio static code analyzer.
Warning message is:
V588 The expression of the 'A =+ B' kind is utilized. Consider reviewing it, as it is possible that 'A += B' was meant. libxml xpath.c 12676

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