Rework after code reading

* Fix possible segfault in `SubPluginFeatures::displayName`
* Minor fixes

include/Plugin.h

@@ -202,19 +202,19 @@ public:
 
 			virtual QString additionalFileExtensions(const Key&) const
 			{
-				return nullptr;
+				return QString();
 			}
 
 			virtual QString displayName(const Key& k) const
 			{
 				return k.isValid()
 					? k.desc->displayName
-					: k.name.toUtf8().data();
+					: k.name;
 			}
 
 			virtual QString description(const Key& k) const
 			{
-				return k.isValid() ? k.desc->description : "";
+				return k.isValid() ? k.desc->description : QString();
 			}
 
 			virtual const PixmapLoader* logo(const Key& k) const

src/core/Plugin.cpp

@@ -127,8 +127,8 @@ QString Plugin::Descriptor::SubPluginFeatures::Key::additionalFileExtensions() c
 	return desc->subPluginFeatures
 		// get from sub plugin
 		? desc->subPluginFeatures->additionalFileExtensions(*this)
-		// get from plugin
-		: nullptr;
+		// no sub plugin, so no *additional* file extensions
+		: QString();
 }
 
 

src/core/PluginFactory.cpp

@@ -180,10 +180,6 @@ void PluginFactory::discoverPlugins()
 				continue;
 			}
 		}
-		else
-		{
-			//qDebug() << "Ignoring" << file.absoluteFilePath() << "(no lmms_plugin_main())";
-		}
 
 		if(pluginDescriptor)
 		{
@@ -199,15 +195,18 @@ void PluginFactory::discoverPlugins()
 					const Plugin::Descriptor::SubPluginFeatures::Key* key = nullptr)
 			{
 				if(!supportedFileTypes.isNull())
-				for (const QString& ext : supportedFileTypes.split(','))
 				{
-					//qDebug() << "Plugin " << info.name() << "supports" << ext;
-					PluginInfoAndKey infoAndKey;
-					infoAndKey.info = info;
-					infoAndKey.key = key
-						? *key
-						: Plugin::Descriptor::SubPluginFeatures::Key();
-					m_pluginByExt.insert(ext, infoAndKey);
+					for (const QString& ext : supportedFileTypes.split(','))
+					{
+						//qDebug() << "Plugin " << info.name()
+						//	<< "supports" << ext;
+						PluginInfoAndKey infoAndKey;
+						infoAndKey.info = info;
+						infoAndKey.key = key
+							? *key
+							: Plugin::Descriptor::SubPluginFeatures::Key();
+						m_pluginByExt.insert(ext, infoAndKey);
+					}
 				}
 			};