[to #42322933]fix gemm demo error when text input is empty

Link: https://code.alibaba-inc.com/Ali-MaaS/MaaS-lib/codereview/10290715

modelscope/models/multi_modal/gemm/gemm_model.py

@@ -67,7 +67,7 @@ class GEMMForMultiModalEmbedding(TorchModel):
         return img_tensor
 
     def parse_text(self, text_str):
-        if text_str is None:
+        if text_str is None or len(text_str) == 0:
             return None
         if isinstance(text_str, str):
             text_ids_tensor = self.gemm_model.tokenize(text_str)
@@ -79,9 +79,12 @@ class GEMMForMultiModalEmbedding(TorchModel):
         return text_ids_tensor.view(1, -1)
 
     def forward(self, input: Dict[str, Any]) -> Dict[str, Any]:
-        image = self.parse_image(input.get('image', input.get('img', None)))
-        text = self.parse_text(input.get('text', input.get('txt', None)))
-        captioning = input.get('captioning', False) is True
+        image_input = input.get('image', input.get('img', None))
+        text_input = input.get('text', input.get('txt', None))
+        captioning_input = input.get('captioning', None)
+        image = self.parse_image(image_input)
+        text = self.parse_text(text_input)
+        captioning = captioning_input is True or text_input == ''
         out = self.gemm_model(image, text, captioning)
         output = {
             OutputKeys.IMG_EMBEDDING: out.get('image_feature', None),