[ci] fix broken ci test with string-keyed dictionary/map

Author: fangq

savejson.m

@@ -593,7 +593,7 @@
     if (isempty(names{i}))
         outcell{idx} = obj2json('x0x0_', val{i}, level + 1, opt);
     else
-        outcell{idx} = obj2json(names{i}, val{i}, level + 1, opt);
+        outcell{idx} = obj2json(char(names{i}), val{i}, level + 1, opt);
     end
     idx = idx + 1;
     if (i < length(names))

test/run_jsonlab_test.m

@@ -108,6 +108,8 @@ function run_jsonlab_test(tests)
                      '{"x0x5F_i":1,"i_":"str"}', 'compact', 1, 'UnpackHex', 0);
     end
     if (exist('containers.Map'))
+        test_jsonlab('containers.Map with string keys', @savejson, containers.Map([string('Andy'), string('^_^')], {true, '-_-'}), ...
+                     '{"Andy":true,"^_^":"-_-"}', 'compact', 1, 'usemap', 1);
         test_jsonlab('containers.Map with char keys', @savejson, containers.Map({'Andy', '^_^'}, {true, '-_-'}), ...
                      '{"Andy":true,"^_^":"-_-"}', 'compact', 1, 'usemap', 1);
         test_jsonlab('containers.Map with number keys', @savejson, containers.Map({1.1, 1.2}, {true, '-_-'}), ...