CppunitTest_starmath_qa_cppunit Failing on Windows with HiDPI screens

[Luke Benes]

After commit: https://cgit.freedesktop.org/libreoffice/core/commit/?id=13894996601d
handle empty Rectangle better in starmath

Windows builds on machines with display scaling enabled are failing. In my testing only a 100% scale factor is working. 

Here is a sample build log with Display Scale = 125%

[build CUT] starmath_qa_cppunit
C:/core/starmath/qa/cppunit/test_node.cxx:88:`anonymous namespace'::NodeTest::testTdf47813
double equality assertion failed
- Expected: 1
- Actual  : 1.02524038461538
- Delta   : 0.02


`anonymous namespace'::Test::viewZoom finished in: 30ms
C:/core/starmath/qa/cppunit/test_node.cxx(88) : error : Assertion
Test name: `anonymous namespace'::NodeTest::testTdf47813
double equality assertion failed
- Expected: 1
- Actual  : 1.02524038461538
- Delta   : 0.02

Failures !!!
Run: 44   Failure total: 1   Failures: 1   Errors: 0

Error: a unit test failed, please do one of:
make CppunitTest_starmath_qa_cppunit CPPUNITTRACE=TRUE # which is a 

Would you like any additional debugging info to track down this problem?

-Luke