Properly handle arrays as candidates for json key.

lib/mbtiles.js

@@ -556,7 +556,10 @@ MBTiles.prototype.putInfo = function(data, callback) {
         // If a data property is a javascript hash/object, slip it into
         // the 'json' field which contains stringified JSON to be merged
         // in at read time. Allows nested/deep metadata to be recorded.
-        if (typeof data[key] === 'object' && !Array.isArray(data[key])) {
+        var nested = typeof data[key] === 'object' &&
+            key !== 'bounds' &&
+            key !== 'center';
+        if (nested) {
             jsondata = jsondata || {};
             jsondata[key] = data[key];
         } else {