virsh: Initialize vshData in cmdMigrate

If the virConnect did not succeeed, we called
virConnectClose on uninitialized data.

Introduced by commit 7eabd55.

tools/virsh-domain.c

@@ -9122,7 +9122,7 @@ cmdMigrate(vshControl *ctl, const vshCmd *cmd)
     bool functionReturn = false;
     int timeout = 0;
     bool live_flag = false;
-    vshCtrlData data;
+    vshCtrlData data = { .dconn = NULL };
 
     if (!(dom = vshCommandOptDomain(ctl, cmd, NULL)))
         return false;