Solved #1584: Warning use of unitialized value (#1585)

script/rvd_front

@@ -3285,7 +3285,7 @@ sub get_execution_machines_limit_per_current_user {
     return login($c) if !_logged_in($c);
 
     my %grants = $USER->grants();
-    my $start_limit = ((exists($grants{'start_limit'})) && ($grants{'start_limit'} > 0)) ? $grants{'start_limit'} : $RAVADA->settings_global()->{'backend'}->{'start_limit'}->{'value'};
+    my $start_limit = ((exists($grants{'start_limit'})) && (defined($grants{'start_limit'})) && ($grants{'start_limit'} > 0)) ? $grants{'start_limit'} : $RAVADA->settings_global()->{'backend'}->{'start_limit'}->{'value'};
     my $can_start_many = $USER->can_start_many ? 1 : 0;
     my @running_domains;