Fix #247 - null pointer on trim current line (#249)

Author: williamdes

lib/import_functions.php

@@ -541,7 +541,7 @@ private function getModifyDetails($lines) {
 						array_merge(array($currentLine),$lines));
 
 				$currentLine = array_shift($lines);
-				if (trim($currentLine))
+				if (is_string($currentLine) && trim($currentLine) !== '')
 					$processline = true;
 			}