handle when a peripheral don't have a _description

Author: sprhawk

cmdebug/svd_gdb.py

@@ -253,7 +253,10 @@ def invoke(self, args, from_tty):
             peripherals = self.svd_device.peripherals
             column_width = max(len(p.name) for p in peripherals) + 2  # padding
             for p in peripherals:
-                desc = re.sub(r'\s+', ' ', p._description)
+                if hasattr(p, "_description"):
+                    desc = re.sub(r'\s+', ' ', p._description)
+                else:
+                    desc = "<No description>"
                 gdb.write("\t{}:{}{}\n".format(p.name, "".ljust(column_width - len(p.name)), desc))
             return