Adding NULL-check.

Author: advait-dixit

mypyc/lib-rt/module_shim.tmpl

@@ -7,6 +7,7 @@ PyInit_{modname}(void)
     if (!(tmp = PyImport_ImportModule("{libname}"))) return NULL;
     PyObject *capsule = PyObject_GetAttrString(tmp, "init_{full_modname}");
     Py_DECREF(tmp);
+    if (capsule == NULL) return NULL;
     void *init_func = PyCapsule_GetPointer(capsule, "{libname}.init_{full_modname}");
     Py_DECREF(capsule);
     if (!init_func) {{