Update code comments and add log warning to help debug

htdocs/core/class/conf.class.php

@@ -156,15 +156,19 @@ class Conf
 
 					if ($value && preg_match('/^MAIN_MODULE_/',$key))
 					{
-						// If this is constant for a new tab page activated by a module.
+						// If this is constant for a new tab page activated by a module. It initializes modules_parts['tabs'].
 						if (preg_match('/^MAIN_MODULE_([0-9A-Z_]+)_TABS_/i',$key))
 						{
 							$partname = 'tabs';
 							$params=explode(':',$value,2);
 							if (! isset($this->modules_parts[$partname]) || ! is_array($this->modules_parts[$partname])) { $this->modules_parts[$partname] = array(); }
-							$this->modules_parts[$partname][$params[0]][]=$value;
+							$this->modules_parts[$partname][$params[0]][]=$value;	// $value may be a string or an array
 						}
-						// If this is constant for all generic part activated by a module
+						// If this is constant for all generic part activated by a module. It initializes
+						// modules_parts['login'], modules_parts['menus'], modules_parts['substitutions'], modules_parts['triggers'], modules_parts['tpl'],
+						// modules_parts['models'], modules_parts['theme']
+						// modules_parts['sms'],
+						// modules_parts['css'], ...
 						elseif (preg_match('/^MAIN_MODULE_([0-9A-Z_]+)_([A-Z]+)$/i',$key,$reg))
 						{
 							$modulename = strtolower($reg[1]);
@@ -176,7 +180,7 @@ class Conf
 							else if (in_array($partname,array('models','theme'))) $value = '/'.$modulename.'/';
 							else if (in_array($partname,array('sms'))) $value = $modulename;
 							else if ($value == 1) $value = '/'.$modulename.'/core/modules/'.$partname.'/';	// ex: partname = societe
-							$this->modules_parts[$partname] = array_merge($this->modules_parts[$partname], array($modulename => $value));
+							$this->modules_parts[$partname] = array_merge($this->modules_parts[$partname], array($modulename => $value));	// $value may be a string or an array
 						}
                         // If this is a module constant (must be at end)
 						elseif (preg_match('/^MAIN_MODULE_([0-9A-Z_]+)$/i',$key,$reg))

htdocs/main.inc.php

@@ -1047,6 +1047,7 @@ function top_htmlhead($head, $title='', $disablejs=0, $disablehead=0, $arrayofjs
         		$filescss=(array) $filescss;	// To be sure filecss is an array
         		foreach($filescss as $cssfile)
         		{
+        			if (empty($cssfile)) dol_syslog("Warning: module ".$modcss." declared a css path file into its descriptor that is empty.", LOG_WARNING);
         			// cssfile is a relative path
 	        		print '<!-- Includes CSS added by module '.$modcss. ' -->'."\n".'<link rel="stylesheet" type="text/css" title="default" href="'.dol_buildpath($cssfile,1);
 	        		// We add params only if page is not static, because some web server setup does not return content type text/css if url has parameters, so browser cache is not used.