t5 model fix

bitsandbytes/nn/modules.py

@@ -190,10 +190,10 @@ class LinearFP4(nn.Linear):
 
         if getattr(self.weight, 'quant_state', None) is None:
             print('FP4 quantization state not initialized. Please call .cuda() or .to(device) on the LinearFP4 layer first.')
-
         inp_dtype = x.dtype
         x = x.to(torch.float16)
-        out = bnb.matmul_fp4(x, self.weight.t(), bias=self.bias.half(), quant_state=self.weight.quant_state)
+        bias = None if self.bias is None else self.bias.half()
+        out = bnb.matmul_fp4(x, self.weight.t(), bias=bias, quant_state=self.weight.quant_state)
         out = out.to(inp_dtype)
 
         return out