Don't call plugin extension functions when opening session files

Without this, the symbol_highlight_provided() function is called
for all the session files which starts LSP servers for all filetypes
of the open files instead of lazily as the file tabs of individual
files get selected.

Author: techee

src/pluginextension.c

@@ -144,7 +144,8 @@ void plugin_extension_unregister(PluginExtension *extension)
  */
 #define CALL_PROVIDED(f, doc, ext)												\
 	G_STMT_START {																\
-		if (main_status.quitting || main_status.closing_all)					\
+		if (main_status.quitting || main_status.closing_all ||					\
+			main_status.opening_session_files)									\
 			return FALSE;														\
 		for (GList *node = all_extensions; node; node = node->next)				\
 		{																		\
@@ -170,7 +171,8 @@ void plugin_extension_unregister(PluginExtension *extension)
  */
 #define CALL_PERFORM(f_provided, doc, f_perform, args, defret)					\
 	G_STMT_START {																\
-		if (main_status.quitting || main_status.closing_all)					\
+		if (main_status.quitting || main_status.closing_all ||					\
+			main_status.opening_session_files)									\
 			return defret;														\
 		for (GList *node = all_extensions; node; node = node->next)				\
 		{																		\