DataFrame from dicts fails with InvalidArgumentError("It is not possible to concatenate arrays of different data types.")

[s-b90]

Polars version checks

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of Polars.

Issue description

When trying to create DF from dicts it may raise an error, even when schema provided.
Note that creating from dict works fine with same example.

pl.DataFrame({'node_groups': [
    [{'nodes': [{'name': 'a', 'time': 0}]}],
    [{'nodes': []}],
]},
    schema={'node_groups': 
         pl.List(
             pl.Struct([
                 pl.Field('nodes', pl.List(
                     pl.Struct([
                         pl.Field('name', pl.Utf8), 
                         pl.Field('time', pl.UInt32)])
                 ))
             ])
         )
        }
    )

node_groups
list[struct[1]]}
[{[{"a",0}]}]
[{[]}]

Reproducible example

import polars as pl
pl.DataFrame([
    {'node_groups': [{'nodes': [{'name': 'a', 'time': 0}]}]},
    {'node_groups': [{'nodes': []}]},
],
    schema={'node_groups': 
         pl.List(
             pl.Struct([
                 pl.Field('nodes', pl.List(
                     pl.Struct([
                         pl.Field('name', pl.Utf8), 
                         pl.Field('time', pl.UInt32)])
                 ))
             ])
         )
        }
    )
PanicException: called `Result::unwrap()` on an `Err` value: InvalidArgumentError("It is not possible to concatenate arrays of different data types.")

Expected behavior

created DataFrame

Installed versions

---Version info---
Polars: 0.16.5
Index type: UInt32
Platform: Linux-5.15.0-60-generic-x86_64-with-glibc2.35
Python: 3.10.6 (main, Nov 14 2022, 16:10:14) [GCC 11.3.0]
---Optional dependencies---
pyarrow: 11.0.0
pandas: 1.5.3
numpy: 1.24.2
fsspec: <not installed>
connectorx: <not installed>
xlsx2csv: <not installed>
deltalake: <not installed>
matplotlib: 3.6.3

[ritchie46]

fixed by #6897