global: start relying on str_free(NULL) being a no-op

Cleanup performed with the following semantic patch:

	@@
	expression E;
	@@

	- if (E != NULL) {
	- 	str_free(&E);
	- }
	+ str_free(&E);

src/imap/imap-fetch.c

@@ -666,8 +666,7 @@ int imap_fetch_end(struct imap_fetch_context *ctx)
 	}
 	ctx->client->output_cmd_lock = NULL;
 
-	if (state->cur_str != NULL)
-		str_free(&state->cur_str);
+	str_free(&state->cur_str);
 
 	i_stream_unref(&state->cur_input);
 

src/lib-fs/fs-metawrap.c

@@ -135,8 +135,7 @@ static void fs_metawrap_file_deinit(struct fs_file *_file)
 
 	if (file->super_read != _file->parent && file->super_read != NULL)
 		fs_file_deinit(&file->super_read);
-	if (file->metadata_header != NULL)
-		str_free(&file->metadata_header);
+	str_free(&file->metadata_header);
 	fs_file_deinit(&_file->parent);
 	i_free(file->file.path);
 	i_free(file);

src/lib-fts/fts-filter.c

@@ -110,8 +110,7 @@ void fts_filter_unref(struct fts_filter **_fpp)
 		fp->v.destroy(fp);
 	else {
 		/* default destroy implementation */
-		if (fp->token != NULL)
-			str_free(&fp->token);
+		str_free(&fp->token);
 		i_free(fp);
 	}
 }

src/lib-http/http-client-request.c

@@ -316,8 +316,7 @@ bool http_client_request_unref(struct http_client_request **_req)
 	}
 	i_stream_unref(&req->payload_input);
 	o_stream_unref(&req->payload_output);
-	if (req->headers != NULL)
-		str_free(&req->headers);
+	str_free(&req->headers);
 	event_unref(&req->event);
 	pool_unref(&req->pool);
 	return FALSE;

src/lib-storage/index/cydir/cydir-sync.c

@@ -143,8 +143,7 @@ int cydir_sync_finish(struct cydir_sync_context **_ctx, bool success)
 	} else {
 		mail_index_sync_rollback(&ctx->index_sync_ctx);
 	}
-	if (ctx->path != NULL)
-		str_free(&ctx->path);
+	str_free(&ctx->path);
 	i_free(ctx);
 	return ret;
 }

src/lib-storage/index/index-search-mime.c

@@ -587,8 +587,7 @@ int index_search_mime_arg_match(struct mail_search_arg *args,
 				       search_mimepart_arg, &mpctx);
 
 	pool_unref(&mpctx.pool);
-	if (mpctx.buf != NULL)
-		str_free(&mpctx.buf);
+	str_free(&mpctx.buf);
 	return ret;
 }
 

src/lib/istream.c

@@ -58,8 +58,7 @@ void i_stream_unref(struct istream **stream)
 	_stream = (*stream)->real_stream;
 
 	if (!io_stream_unref(&_stream->iostream)) {
-		if (_stream->line_str != NULL)
-			str_free(&_stream->line_str);
+		str_free(&_stream->line_str);
 		i_stream_snapshot_free(&_stream->prev_snapshot);
 		i_stream_unref(&_stream->parent);
 		io_stream_free(&_stream->iostream);

src/login-common/client-common.c

@@ -302,8 +302,7 @@ void client_destroy(struct client *client, const char *reason)
 
 	timeout_remove(&client->to_disconnect);
 	timeout_remove(&client->to_auth_waiting);
-	if (client->auth_response != NULL)
-		str_free(&client->auth_response);
+	str_free(&client->auth_response);
 
 	if (client->proxy_password != NULL) {
 		safe_memset(client->proxy_password, 0,

src/plugins/acl/acl-attributes.c

@@ -241,8 +241,7 @@ int acl_attribute_iter_deinit(struct mailbox_attribute_iter *iter)
 		mail_storage_set_internal_error(aiter->iter.box->storage);
 		ret = -1;
 	}
-	if (aiter->acl_name != NULL)
-		str_free(&aiter->acl_name);
+	str_free(&aiter->acl_name);
 	i_free(aiter);
 	return ret;
 }

src/plugins/fts-solr/fts-backend-solr.c

@@ -410,10 +410,8 @@ fts_backend_solr_update_deinit(struct fts_backend_update_context *_ctx)
 			ret = -1;
 	}
 
-	if (ctx->cmd != NULL)
-		str_free(&ctx->cmd);
-	if (ctx->cmd_expunge != NULL)
-		str_free(&ctx->cmd_expunge);
+	str_free(&ctx->cmd);
+	str_free(&ctx->cmd_expunge);
 	array_foreach_modifiable(&ctx->fields, field) {
 		str_free(&field->value);
 		i_free(field->key);