Fix potential crash if no any plugins present

Thanks to Roman Savochenko for the patch!
(cherry picked from commit 31eb731cab)

kbfxlib/data/kbfxplasmapluginloader.cpp

@@ -103,7 +103,7 @@ KbfxPlasmaPluginLoader::getView ( TQString name )
 		pluginMap().remove ( it );
 	}
 	init();
-	KbfxDataStack * stack = pluginMap() [name]->data();
+	KbfxDataStack * stack = pluginMap() [name] ? pluginMap() [name]->data() : NULL;
 	
         if (stack == 0 ) {
             return new KbfxDataStack();