exclude call of compute_bootdisk_size method with new_size=None

library/decort_kvmvm.py

@@ -624,7 +624,11 @@ class decort_kvmvm(DecortController):
         Note that it does not modify power state of KVM VM.
         """
         self.compute_networks(self.comp_info, self.amodule.params['networks'])
-        self.compute_bootdisk_size(self.comp_info, self.amodule.params['boot_disk'])
+
+        boot_disk_new_size = self.amodule.params['boot_disk']
+        if boot_disk_new_size:
+            self.compute_bootdisk_size(self.comp_info, boot_disk_new_size)
+            
         self.compute_data_disks(self.comp_info, self.amodule.params['data_disks'])
         self.compute_resize(self.comp_info,
                             self.amodule.params['cpu'], self.amodule.params['ram'],