[5.6] Fix issue with Resources when loading a single MergeValue with an associative array

[themsaid]

No description provided.

[Astyk]

Just note, that parameter '$numericKey' doesn't count anymore

[hotmeteor]

This is a breaking change for how array keys are resolved.

array:6 [
  1 => 0
  2 => 0
  3 => 0
  4 => 0
  5 => 0
  "total" => 0
]

Before the change the above array could be returned from the resource. After, the array is formatted as:

array:6 [
  0 => 0
  1 => 0
  2 => 0
  3 => 0
  4 => 0
  5 => 0
]