modules: simplify vlc_module_match() error handling

Set the modules table to NULL on error, to simplify call sites.

include/vlc_modules.h

@@ -46,7 +46,7 @@ struct vlc_logger;
  * \param names string of comma-separated requested module shortcut names
  * \param strict whether to exclude modules with no unmatching shortcut names
  * \param modules storage location for the base address of a sorted table
- *                of candidate modules [OUT]
+ *                of candidate modules (NULL on error) [OUT]
  * \param strict_matches storage location for the count of strictly matched
  *                       modules [OUT]
  * \return number of modules found or a strictly negative value on error

src/modules/modules.c

@@ -112,17 +112,18 @@ ssize_t vlc_module_match(const char *capability, const char *names,
     module_t **sorted = malloc(total * sizeof (*sorted));
     size_t matches = 0;
 
-    *modules = sorted;
-
     if (total > 0) {
         if (unlikely(unsorted == NULL || sorted == NULL)) {
             free(unsorted);
             free(sorted);
+            *modules = NULL;
             return -1;
         }
         memcpy(unsorted, tab, total * sizeof (*unsorted));
     }
 
+    *modules = sorted;
+
     /* Go through the list of module shortcut names. */
     while (names[0] != '\0') {
         const char *shortcut = names;