FS-4860 --resolve This seems to have come from a malformed file_string in the ringback var

src/mod/applications/mod_dptools/mod_dptools.c

@@ -4476,8 +4476,13 @@ static switch_status_t next_file(switch_file_handle_t *handle)
 		} else {
 			switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_ERROR, "Error finding the folder path section in '%s'\n", path);
 		}
+	}
 
+	if (switch_file_exists(file, handle->memory_pool) != SWITCH_STATUS_SUCCESS) {
+		switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_ERROR, "File [%s] does not exist.\n", file);
+		goto top;
 	}
+
 	if (switch_core_file_open(&context->fh, file, handle->channels, handle->samplerate, handle->flags, NULL) != SWITCH_STATUS_SUCCESS) {
 		goto top;
 	}

src/switch_core_file.c

@@ -76,6 +76,10 @@ SWITCH_DECLARE(switch_status_t) switch_core_perform_file_open(const char *file,
 		switch_set_flag(fh, SWITCH_FILE_FLAG_FREE_POOL);
 	}
 
+	if (switch_directory_exists(file_path, fh->memory_pool) == SWITCH_STATUS_SUCCESS) {
+		switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_ERROR, "File [%s] is a directory not a file.\n", file_path);
+		goto fail;
+	}
 
 	if ((rhs = strstr(file_path, SWITCH_URL_SEPARATOR))) {
 		switch_copy_string(stream_name, file_path, (rhs + 1) - file_path);
@@ -198,6 +202,8 @@ SWITCH_DECLARE(switch_status_t) switch_core_perform_file_open(const char *file,
 
   fail:
 
+	switch_clear_flag(fh, SWITCH_FILE_OPEN);
+
 	if (switch_test_flag(fh, SWITCH_FILE_FLAG_FREE_POOL)) {
 		switch_core_destroy_memory_pool(&fh->memory_pool);
 	}