Need help in correction of error for training my data

Error using vision.internal.cnn.validation.checkGroundTruth>classHasNoBoxes (line 19)
Cell contents reference from a non-cell array object.

Error in vision.internal.cnn.validation.checkGroundTruth (line 9)
    if classHasNoBoxes(gt(:,i))

Error in vision.internal.rcnn.parseInputs (line 4)
vision.internal.cnn.validation.checkGroundTruth(trainingData, fname);

Error in trainRCNNObjectDetector (line 185)
params = vision.internal.rcnn.parseInputs(trainingData, network, options, mfilename, varargin{:});
.
Error in RCNNmyImplementation (line 60)
rcnn = trainRCNNObjectDetector(stopSigns, layers, options);

Answer 1

[per isakson]

The message says:

Cell contents reference from a non-cell array object

An example of this error

>> a=17;
>> a{1}
Cell contents reference from a non-cell array object. 
>>

I guess that somewhere in the input arguments of trainRCNNObjectDetector there is a value that is supposed to be a cell array but is something else.