Settings: set FIU_NUM to the actual number of FIUs

Even in the case the number of FIUs stored in the settings file (FIU_NUM)
differs from the actual number of FIUs therein, set it to the actual value.
This essential degrades it to a simple size value of the respective fius
array but avoids any confusion in the code.

bin/FIJI/Settings.pm

@@ -350,9 +350,8 @@ sub read_settingsfile ($$$) {
         $logger->warn($msg);
         $warnings = defined($warnings) ? "$warnings\n" : "";
         $warnings .= "$msg\n";
-    } else {
-        $design_ref->{'FIU_NUM'} = $fiu_num;    # assume the best if FIU_NUM constant is not given
     }
+    $design_ref->{'FIU_NUM'} = $fiu_num; # assume the best if FIU_NUM constant is not given or misleading
 
     my $dups = $fiji_settings_ref->determine_duplicate_fiu_nets();
     my @dup_nets = keys(%{$dups});