poppler-0.58 breaks inkscape build

[Thomas Klausner]

Building inkscape-0.92.1 with poppler-0.59 fails:

```
.../inkscape/work/inkscape-0.92.1/src/extension/internal/pdfinput/pdf-parser.cpp: In member function 'void PdfParser::parse(Object*, GBool)':
.../inkscape/work/inkscape-0.92.1/src/extension/internal/pdfinput/pdf-parser.cpp:417:29: error: invalid conversion from 'Object*' to 'int' [-fpermissive]
       obj->arrayGet(i, &obj2);
... ^
````
(2000 more lines, see attachment)

This is another occurrence of breakage due to using the non-public API, see https://bugs.launchpad.net/inkscape/+bug/239544

[Patrick Storz (ede123)]

I committed a fix by David to master yesterday:
https://gitlab.com/inkscape/inkscape/commit/9418824967eb4c53371ef8588243fed4cab496e0

If no issues are found I plan to back-port it to the 0.92.x branch eventually.

[Patrick Storz (ede123)]

Now also committed to 0.92.x in
https://gitlab.com/inkscape/inkscape/commit/93ccf03162cd2e46d962822d5507865f3451168c