Fix validation of non-number keys in array validation (#118)

Closes #117 
* Fix validation of non-number keys in array validation
* Add test case

Author: olegrok

avro_schema/frontend.lua

@@ -878,8 +878,11 @@ copy_data = function(stack, schema, data, visited)
                 end
             end
         elseif schematype == 'array'  then
-            for i, v in ipairs(data) do
+            for i, v in pairs(data) do
                 stack.ptr[frame_no] = i
+                if type(i) ~= 'number' then
+                    error('@Non-number array key', 0)
+                end
                 res[i] = copy_data(stack, schema.items, v, visited)
             end
         elseif schematype == 'map'    then

test/ddt_suite/validate.lua

@@ -305,6 +305,12 @@ t {
     validate_error = '6: Not a int: XXX'
 }
 
+t {
+    schema = array,
+    validate = '{"key":"value"}',
+    validate_error = 'key: Non-number array key'
+}
+
 -- map
 
 local map = '{"type":"map","values":"int"}'