* f2b_*_destroy() : fixes

src/backend.c

@@ -121,8 +121,11 @@ f2b_backend_init(f2b_backend_t *backend, f2b_config_section_t *config) {
 void
 f2b_backend_destroy(f2b_backend_t *backend) {
   if (!backend) return;
-  backend->destroy(backend->cfg);
-  dlclose(backend->h);
+  if (backend->h) {
+    if (backend->cfg)
+      backend->destroy(backend->cfg);
+    dlclose(backend->h);
+  }
   free(backend);
 }
 

src/filter.c

@@ -180,8 +180,11 @@ f2b_filter_init(f2b_filter_t *filter, f2b_config_section_t *config) {
 void
 f2b_filter_destroy(f2b_filter_t *filter) {
   if (!filter) return;
-  filter->destroy(filter->cfg);
-  dlclose(filter->h);
+  if (filter->h) {
+    if (filter->cfg)
+      filter->destroy(filter->cfg);
+    dlclose(filter->h);
+  }
   free(filter);
 }
 

src/source.c

@@ -117,8 +117,11 @@ f2b_source_init(f2b_source_t *source, f2b_config_section_t *config) {
 void
 f2b_source_destroy(f2b_source_t *source) {
   if (!source) return;
-  source->destroy(source->cfg);
-  dlclose(source->h);
+  if (source->h) {
+    if (source->cfg)
+      source->destroy(source->cfg);
+    dlclose(source->h);
+  }
   free(source);
 }