check annotation category not cat collection

[JoshRice1]

When doing a merge the cid the wrong id was being checked to determine if it should be merged.

To recreate:
Create json file with the
"categories": [
{
"id": 1,
"name": "cat-1",
"supercategory": ""
},
{
"id": 2,
"name": "cat-2",
"supercategory": ""
},
{
"id": 3,
"name": "cat-3",
"supercategory": ""
}
]
Create a second with:
"categories": [
{
"id": 1,
"name": "cat-1",
"supercategory": ""
},
{
"id": 2,
"name": "cat-6",
"supercategory": ""
},
{
"id": 3,
"name": "cat-3",
"supercategory": ""
}
]

Then merget the two with -c 1 2 3 from the first and -c 1 3 from the second.