report-missing-inputs: treat empty inputs as unset (#6)

Note that missing secrets are a common case of empty inputs

scripts/report-missing-inputs.pl

@@ -31,7 +31,7 @@ sub get_from_json_env {
         if (/^  (\S+):/) {
             $key = $1;
         } elsif (/^    required: true/) {
-            push @required, $key unless %inputs && defined $inputs{$key};
+            push @required, $key unless %inputs && defined $inputs{$key} && $inputs{key} =~ /./;
         }
     }
 }