fix: correct convertation arg to tensor array

Author: atellmer

tfjs-core/src/tensor_util_env.ts

@@ -133,12 +133,18 @@ export function convertToTensor<T extends Tensor>(
 export function convertToTensorArray<T extends Tensor>(
     arg: Array<T|TensorLike>, argName: string, functionName: string,
     parseAsDtype: DataType|'numeric'|'string_or_numeric' = 'numeric'): T[] {
+  let tensors = arg as T[];
+
   if (!Array.isArray(arg)) {
-    throw new Error(
-        `Argument ${argName} passed to ${functionName} must be a ` +
-        '`Tensor[]` or `TensorLike[]`');
+    if ((arg as T) instanceof getGlobalTensorClass()) {
+      tensors = [arg];
+    } else {
+      throw new Error(
+          `Argument ${argName} passed to ${functionName} must be a ` +
+          '`Tensor[]` or `TensorLike[]`');
+      }
   }
-  const tensors = arg as T[];
+
   return tensors.map(
       (t, i) =>
           convertToTensor(t, `${argName}[${i}]`, functionName, parseAsDtype));