IPFIX output: fix integer division by zero when creating a file

If the window alignment was enabled but the window size was zero
(both are default values), the collector crashed due to division
by zero. This fix ignores the alignment if the windows size is zero.

Author: Lukas Hutak

src/plugins/output/ipfix/src/IPFIXOutput.cpp

@@ -88,7 +88,7 @@ IPFIXOutput::new_file(const std::time_t current_time)
     close_file();
 
     // Get the timestamp of the file to create
-    if (config->align_windows) {
+    if (config->window_size > 0 && config->align_windows) {
         // Round down to the nearest multiple of window size
         file_start_time = (current_time / config->window_size) * config->window_size;
     } else {