AC: allow empty text b for text classification (#3182)

Author: eaidova

tools/accuracy_checker/openvino/tools/accuracy_checker/annotation_converters/text_classification.py

@@ -107,7 +107,10 @@ def read_annotation(self):
                 guid = "dev-{}".format(idx)
                 label = self.reversed_label_map[line[self.label_ind]]
                 text_a = line[self.text_a_ind]
-                text_b = line[self.text_b_ind] if self.text_b_ind is not None else None
+                text_b = (
+                    line[self.text_b_ind]
+                    if self.text_b_ind is not None and len(line) > self.text_b_ind else None
+                )
                 lines.append(InputExample(guid, text_a, text_b, label))
 
         return lines