Fix: typo error

htdocs/core/lib/pdf.lib.php

@@ -78,7 +78,7 @@ function pdf_getInstance($format='',$metric='mm',$pagetype='P')
 	global $conf;
 
 	if (! empty($conf->global->MAIN_USE_FPDF) && ! empty($conf->global->MAIN_DISABLE_FPDI))
-    	return "Error MAIN_USE_PDF and MAIN_DISABLE_FPDI can't be set together";
+    	return "Error MAIN_USE_FPDF and MAIN_DISABLE_FPDI can't be set together";
 
 	// We use by default TCPDF
 	if (empty($conf->global->MAIN_USE_FPDF)) require_once(TCPDF_PATH.'tcpdf.php');