Prevent an OOB read in expand_dims.cc

The for loop that follows this check assumes that `axis` is between `0` and `input_dims.size`. If user supplied `axis` is negative, the if code before this check is supposed to bring it back to positive (similar to how in Python one can do `l[-3]` to mean `l[-3 + len(l)]`).

PiperOrigin-RevId: 387200206
Change-Id: I162f4feba12d547c3a4340833ae682016a2ebfab

tensorflow/lite/kernels/expand_dims.cc

@@ -37,6 +37,7 @@ TfLiteStatus ExpandTensorDim(TfLiteContext* context, const TfLiteTensor& input,
     axis = input_dims.size + 1 + axis;
   }
   TF_LITE_ENSURE(context, axis <= input_dims.size);
+  TF_LITE_ENSURE(context, axis >= 0);
 
   TfLiteIntArray* output_dims = TfLiteIntArrayCreate(input_dims.size + 1);
   for (int i = 0; i < output_dims->size; ++i) {