tests: null terminate too long string and add test for unterminated string

tests/tests_unit.c

@@ -162,9 +162,16 @@ START_TEST(semantic_path_unit_test) {
   char too_long[XR_MAX_PATH_LENGTH + 1];
   memset(too_long, 'a', XR_MAX_PATH_LENGTH + 1);
   too_long[0] = '/';
+  too_long[XR_MAX_PATH_LENGTH] = '\0';
   ck_assert_int_eq(oxr_xrStringToPath(oxr.instance, too_long, &path),
                    XR_ERROR_PATH_FORMAT_INVALID);
 
+  char unterminated[XR_MAX_PATH_LENGTH];
+  memset(unterminated, 'a', XR_MAX_PATH_LENGTH);
+  unterminated[0] = '/';
+  ck_assert_int_eq(oxr_xrStringToPath(oxr.instance, unterminated, &path),
+                   XR_ERROR_PATH_FORMAT_INVALID);
+
   ck_assert_int_eq(
       oxr_xrStringToPath(oxr.instance, "/ascii/0123/-/_/foobar", &path),
       XR_SUCCESS);