multi_heap: ensure that malloc(0) return NULL pointer in any poisoning configuration

components/heap/test/test_aligned_alloc_caps.c

@@ -159,4 +159,11 @@ TEST_CASE("Capabilities aligned calloc test", "[heap]")
     } 
 #endif
 
-}
+}
+
+TEST_CASE("aligned_alloc(0) should return a NULL pointer", "[heap]")
+{
+    void *p;
+    p = heap_caps_aligned_alloc(32, 0, MALLOC_CAP_DEFAULT);
+    TEST_ASSERT(p == NULL);
+}