Upgrade fails if a file in usageEventLogs is empty about pkp-lib

[SydneyUni-Jim]

convert in PKP\cliTool\traits\ConvertLogFile initially set $isSuccessful to false and only sets it to true once it has successfully converted an entry.

pkp-lib/classes/cliTool/traits/ConvertLogFile.php

Lines 131 to 132 in c111708

	$isSuccessful = false;
	while (!feof($fhandle)) {

pkp-lib/classes/cliTool/traits/ConvertLogFile.php

Lines 225 to 226 in c111708

	$isSuccessful = true;
	}

This logic fails if:

• the file's size is zero and feof(…) immediately returns false; or
• the while loop never gets to its end because all of the lines trigger one of the continue statements

[SydneyUni-Jim]

Relate to handling of $isSuccessful, after the first successful entry sets $isSuccessful to true it is never set back to false. This means the I8508_ConvertCurrentLogFile migration passes if and whenever at least one log entry is successfully converted.

The logics like this don't set $isSuccessful back to false.

pkp-lib/classes/cliTool/traits/ConvertLogFile.php

Lines 142 to 145 in c111708

	if (!$this->isLogEntryValid($entryData)) {
	fwrite(STDERR, "Invalid log entry at line {$lineNumber}." . PHP_EOL);
	continue;
	}

[bozana]

Hi @SydneyUni-Jim,
Yes, I think we need to somehow consider -- at least report it correctly -- if the file is empty (also in case only continue statements are called).
But, else, if any other problem occurs (like invalid line) I think it is OK: we convert the lines that can be converted and report the existing issues, so that user can act as needed.