Fix issue with mul_back that not check input size.

lib/nnc/cmd/blas/mps/ccv_nnc_mul_mps.m

@@ -114,13 +114,13 @@ static int _ccv_nnc_mul_back(const ccv_nnc_cmd_t cmd, const ccv_nnc_hint_t hint,
 
 	const float p = cmd.info.blas.a[0];
 	const ccv_nnc_tensor_view_t* const g = (const ccv_nnc_tensor_view_t*)inputs[0] ? : 0;
-	const ccv_nnc_tensor_view_t* const b1 = (const ccv_nnc_tensor_view_t*)inputs[2];
-	ccv_nnc_tensor_view_t* const b2 = (ccv_nnc_tensor_view_t*)inputs[1];
+	const ccv_nnc_tensor_view_t* const b1 = (input_size >= 3) ? (const ccv_nnc_tensor_view_t*)inputs[2] : 0;
+	ccv_nnc_tensor_view_t* const b2 = (input_size >= 2) ? (ccv_nnc_tensor_view_t*)inputs[1] : 0;
 
 	ccv_nnc_tensor_view_t* const a = (ccv_nnc_tensor_view_t*)outputs[0];
 	ccv_nnc_tensor_view_t* const h = output_size > 1 ? (ccv_nnc_tensor_view_t*)outputs[1] : 0;
-	const int b2_nd = ccv_nnc_tensor_nd(b1->info.dim);
-	const int b1_nd = ccv_nnc_tensor_nd(b2->info.dim);
+	const int b2_nd = b2 ? ccv_nnc_tensor_nd(b2->info.dim) : 0;
+	const int b1_nd = b1 ? ccv_nnc_tensor_nd(b1->info.dim) : 0;
 	const int g_nd = ccv_max(b2_nd, b1_nd);
 	const int offset = CCV_NNC_MAX_DIM + 2 - g_nd;
 	if (a)
@@ -131,9 +131,10 @@ static int _ccv_nnc_mul_back(const ccv_nnc_cmd_t cmd, const ccv_nnc_hint_t hint,
 
 	@autoreleasepool {
 		NSMutableArray<NSNumber*>* mps_g_shape = [[NSMutableArray new] autorelease];	
-		for (int i = offset; i < CCV_NNC_MAX_DIM + 2; i++){
+		for (int i = offset; i < CCV_NNC_MAX_DIM + 2; i++)
+		{
 			[mps_g_shape addObject:@(gdim[i])]; // still need mps_g_shape for target broadcast shape
-			gdim[i-offset] = gdim[i]; // move forward to align info.dim format 
+			gdim[i - offset] = gdim[i]; // move forward to align info.dim format 
 		}               
 		const int* gdim_a = gdim;