syntax errors in meshlabplugins/filter_screened_poisson

[rmathar]

Syntax errors in meshlab-2023.12 in the meshlabplugins/filter_screened_poisson directory are patched in

https://build.opensuse.org/projects/home:rjmathar/packages/meshlab/files/sparseMatrix.patch?expand=1

There are 4 places where a non-existing member p.value of a class is used, and one case where
an obviously non-used function tries to access non-existing members through a this pointer.
The errors are easily revealed by trying to compile the source code under the openSUSE gcc compiler.