More exhaustive layergroup validation:

- layers is an array and it's not empty
- layers has at least options

lib/cartodb/template_maps.js

@@ -138,8 +138,22 @@ function isInvalidLayergroup(layergroup) {
         return new Error('Missing layergroup');
     }
 
-    if (!_.isArray(layergroup.layers)) {
-        return new Error('Missing layers array from layergroup config');
+    var layers = layergroup.layers;
+
+    if (!_.isArray(layers) || layers.length === 0) {
+        return new Error('Missing or empty layers array from layergroup config');
+    }
+
+    var invalidLayers = layers
+        .map(function(layer, layerIndex) {
+            return layer.options ? null : layerIndex;
+        })
+        .filter(function(layerIndex) {
+            return layerIndex !== null;
+        });
+
+    if (invalidLayers.length) {
+        return new Error('Missing `options` in layergroup config for layers: ' + invalidLayers.join(', '));
     }
 
     return false;