DataAnalyzer with `histogram_only=True`

[wyli]

Describe the bug
using DataAnalyzer with histogram_only=True raises error:

2023-08-15 15:15:52,439 - INFO - Found 0 GPUs for data analyzing!
2023-08-15 15:15:52,441 - INFO - device=cuda:0 but CUDA device is not available, using CPU instead.
  0%|                                                                                                                                                      | 0/10 [00:08<?, ?it/s]
Traceback (most recent call last):
  File "/workspace/demo21/data/analyzer.py", line 184, in <module>
    datastas = analyzer.get_all_case_stats(transform_list=label_transform)
  File "/usr/local/lib/python3.10/dist-packages/monai/apps/auto3dseg/data_analyzer.py", line 228, in get_all_case_stats
    result_bycase = self._get_all_case_stats(0, 1, None, key, transform_list)
  File "/usr/local/lib/python3.10/dist-packages/monai/apps/auto3dseg/data_analyzer.py", line 359, in _get_all_case_stats
    DataStatsKeys.BY_CASE_IMAGE_PATH: d[DataStatsKeys.BY_CASE_IMAGE_PATH],
KeyError: image_filepath

the root cause is that when skipping certain analyzers, the output stats keys won't exist

MONAI/monai/auto3dseg/seg_summarizer.py

Lines 103 to 106 in 5833b1c

	if not self.histogram_only:
	self.add_analyzer(FilenameStats(image_key, DataStatsKeys.BY_CASE_IMAGE_PATH), None)
	self.add_analyzer(FilenameStats(label_key, DataStatsKeys.BY_CASE_LABEL_PATH), None)
	self.add_analyzer(ImageStats(image_key), ImageStatsSumm(average=average))

but the _get_all_case_stats assumes the stats keys

MONAI/monai/apps/auto3dseg/data_analyzer.py

Lines 358 to 362 in 5833b1c

	stats_by_cases = {
	DataStatsKeys.BY_CASE_IMAGE_PATH: d[DataStatsKeys.BY_CASE_IMAGE_PATH],
	DataStatsKeys.BY_CASE_LABEL_PATH: d[DataStatsKeys.BY_CASE_LABEL_PATH],
	DataStatsKeys.IMAGE_STATS: d[DataStatsKeys.IMAGE_STATS],
	}