[tex4ht] "page is empty" messages. But nothing seems wrong in the HTML

[Nasser M. Abbasi]

I am just curious, why sometimes I see, when compiling
with tex4ht, using SVG for math, messages that says

   processing page nnnnn
   page is empty   ------>

I see so many of them. Interspersed between not empty pages.

I am now compiling one large file and seeing these. But I see
them on many other files, just thought to ask. I can provide
more information.

The strange thing, I see nothing wrong in the HTML so far, but
this produces hundreds of web pages with lots of math and I could
have missed something. There are no errors, compile completes OK.

Can one ignore such messages? have others seen them? Why
they show up? Here is example

"processing page 11399
   graphic size: 2570.18pt x 40.2412pt (903.315mm x 14.1432mm)
   output written to report-11399.svg
processing page 11400
   page is empty
   graphic size: 0pt x 0pt (0mm x 0mm)
   output written to report-11400.svg
processing page 11401
   graphic size: 348.8pt x 18.8627pt (122.589mm x 6.62948mm)
   output written to report-11401.svg
processing page 11402
   graphic size: 1436.85pt x 45.4672pt (504.995mm x 15.9799mm)
   output written to report-11402.svg
processing page 11403
   page is empty
   graphic size: 0pt x 0pt (0mm x 0mm)
   output written to report-11403.svg
....
processing page 12211
   page is empty
   graphic size: 0pt x 0pt (0mm x 0mm)
   output written to report-12211.svg
processing page 12212
   graphic size: 1461.2pt x 35.8913pt (513.555mm x 12.6144mm)
   output written to report-12212.svg
processing page 12213
   page is empty
   graphic size: 0pt x 0pt (0mm x 0mm)
   output written to report-12213.svg
....
processing page 13331
   page is empty
   graphic size: 0pt x 0pt (0mm x 0mm)
   output written to report-13331.svg
13331 of 13331 pages converted in 5515.39 seconds
Make4ht: tex4ht  -cmozhtf -utf8 "report.dvi" can be executed only 1x
Make4ht: t4ht  -p "report.dvi" can be executed only 1x
Parse LG
mv report-00002.svg re0x.svg
mv report-00003.svg re1x.svg
.....
"

The above phase of the compile is the one that takes for ever.
Sometimes 1 or 2 or more hrs on some large files, just seeing
these "processing page ..." messages scrolling on the
screen until tex4ht is done.

So trying to see if there is something I could do to speed it up
and if the empty pages thing has anything to do with it.

Using latest tex4ht and texlive 2017.

Thanks
--Nasser