fix memory corruption issue

see https://gist.github.com/keltecc/49da037072276f21b005a8337c15db26
for details on the issue

verified by running proof of concept against fix -
> python poc.py
3.11.0 (main, Nov 24 2022, 13:13:19) [Clang 13.1.6 (clang-1316.0.21.2.5)]
X: 0x0
Y: 0x0
(On curve <MyCurve>)
<POINT AT INFINITY>

pyproject.toml

@@ -19,6 +19,7 @@ classifiers = [
     "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
+    "Programming Language :: Python :: 3.12",
     "Operating System :: MacOS :: MacOS X",
     "Operating System :: POSIX :: Linux"
 ]

src/curveMath.c

@@ -215,6 +215,7 @@ static PyObject * curvemath_mul(PyObject *self, PyObject *args) {
     }
 
     PointZZ_p result;
+    mpz_inits(result.x, result.y, NULL);
     mpz_t scalar;
     mpz_init_set_str(scalar, d, 10);
     CurveZZ_p * curve = buildCurveZZ_p(p, a, b, q, gx, gy, 10);;