Regarding crnn model

Hi, can anyone please help me in resolving this issue :

I’m implementing CRNN model, i have developed the model and the output of the RNN was [1,26, 129], and i have got trouble in implementing CTC, however somehow i have did this

here the problem is the model is not back propagationg it is showing this error :

I tried many ways but couldn’t resolve this, kindly help in resolving this issue.