Avoid generating an exception if there are no generic power domain(s)
registered:

(gdb) lx-genpd-summary
domain                          status          children
    /device                                             runtime status
----------------------------------------------------------------------
Python Exception <class 'gdb.error'>: No symbol "gpd_list" in current context.
Error occurred in Python: No symbol "gpd_list" in current context.
(gdb) quit

Fixes: 8207d4a88e1e ("scripts/gdb: add lx-genpd-summary command")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
Changes in v2:

- correctly invoke gdb_eval_or_none

 scripts/gdb/linux/genpd.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/scripts/gdb/linux/genpd.py b/scripts/gdb/linux/genpd.py
index 39cd1abd8559..b53649c0a77a 100644
--- a/scripts/gdb/linux/genpd.py
+++ b/scripts/gdb/linux/genpd.py
@@ -5,7 +5,7 @@
 import gdb
 import sys
 
-from linux.utils import CachedType
+from linux.utils import CachedType, gdb_eval_or_none
 from linux.lists import list_for_each_entry
 
 generic_pm_domain_type = CachedType('struct generic_pm_domain')
@@ -70,6 +70,8 @@ Output is similar to /sys/kernel/debug/pm_genpd/pm_genpd_summary'''
             gdb.write('    %-50s  %s\n' % (kobj_path, rtpm_status_str(dev)))
 
     def invoke(self, arg, from_tty):
+        if gdb_eval_or_none("&gpd_list") is None:
+            raise gdb.GdbError("No power domain(s) registered")
         gdb.write('domain                          status          children\n');
         gdb.write('    /device                                             runtime status\n');
         gdb.write('----------------------------------------------------------------------\n');
-- 
2.34.1