instance update: fixing no err check after creating client (#657)

# Description
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If we fail to create the client, this will result in a SIGSEV when using
it

## Checklist
(For exoscale contributors)

* [x] Changelog updated (under *Unreleased* block)
* [x] Testing

## Testing

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Describe the tests you did
-->

CHANGELOG.md

@@ -1,4 +1,10 @@
 # Changelog
+
+## Unreleased
+
+### Bug fixes
+- instance update: fixing no err check after creating client #657
+
 ## 1.82.0
 
 ### Features

cmd/instance_update.go

@@ -103,6 +103,9 @@ func (c *instanceUpdateCmd) cmdRun(cmd *cobra.Command, _ []string) error {
 			if cmd.Flags().Changed(mustCLICommandFlagName(c, &c.Protection)) {
 				var client *v3.Client
 				client, err = switchClientZoneV3(ctx, globalstate.EgoscaleV3Client, v3.ZoneName(c.Zone))
+				if err != nil {
+					return
+				}
 
 				var instanceID v3.UUID
 				var op *v3.Operation