Categoricals: Accept null pointer as subject.

Previously, certain functions would crash, or behave badly if their
argument was NULL.  This change makes them do nothing, or return
default values, as appropriate.  This saves callers having to always
test for NULL.

diff --git a/src/math/categoricals.c b/src/math/categoricals.c
index 2a0d4f85ba9e000fb1e4ac36e5d37684f4d2a389..fdd552fed58d3c08d7a95d27f471ef9257296f69 100644 (file)
--- a/src/math/categoricals.c
+++ b/src/math/categoricals.c
@@ -358,6 +358,10 @@ categoricals_update (struct categoricals *cat, const struct ccase *c)
 {
   int i;
   struct variable_node *vn = NULL;
+
+  if (NULL == cat)
+    return;
+
   const double weight = cat->wv ? case_data (c, cat->wv)->f : 1.0;
 
   assert (NULL == cat->reverse_variable_map_short);
@@ -453,6 +457,9 @@ categoricals_n_total (const struct categoricals *cat)
 size_t
 categoricals_df_total (const struct categoricals *cat)
 {
+  if (NULL == cat)
+    return 0;
+
   return cat->df_sum;
 }
 
@@ -479,6 +486,10 @@ categoricals_done (const struct categoricals *cat_)
   int i;
   int idx_short = 0;
   int idx_long = 0;
+
+  if (NULL == cat)
+    return;
+
   cat->df_sum = 0;
   cat->n_cats_total = 0;