… with image_list_file_path (#3478)
If we try to load a pre-3.12 (pre sensor rig support) db, and we also
pass `--image_list_path`, the db loading will fail mainly due to the
lines I am removing in this PR. Not sure why we have those in there.
The error that pops up without this change:
```
I20250711 11:43:48.726486 140208169588800 incremental_pipeline.cc:253] Loading database
I20250711 11:43:48.728317 140208169588800 database_cache.cc:66] Loading rigs...
I20250711 11:43:48.728328 140208169588800 database_cache.cc:76]  0 in 0.000s
I20250711 11:43:48.728333 140208169588800 database_cache.cc:84] Loading cameras...
I20250711 11:43:48.728343 140208169588800 database_cache.cc:102]  1 in 0.000s
I20250711 11:43:48.728346 140208169588800 database_cache.cc:110] Loading frames...
I20250711 11:43:48.728351 140208169588800 database_cache.cc:127]  0 in 0.000s
I20250711 11:43:48.728355 140208169588800 database_cache.cc:135] Loading matches...
I20250711 11:43:48.756288 140208169588800 database_cache.cc:140]  9644 in 0.028s
I20250711 11:43:48.756310 140208169588800 database_cache.cc:156] Loading images...
terminate called after throwing an instance of 'std::out_of_range'
  what():  unordered_map::at
*** Aborted at 1752227028 (unix time) try "date -d @1752227028" if you are using GNU date ***
PC: @     0x7f84c62ef00b signal
```
The actual error is coming from here:
```
        const frame_t frame_id1 = image_to_frame_id.at(image_id1);
        const frame_t frame_id2 = image_to_frame_id.at(image_id2);
```
line 205, 206
---------
Co-authored-by: Shaohui Liu <b1ueber2y@gmail.com>
Co-authored-by: Johannes Schönberger <jsch@demuc.de>
Co-authored-by: Johannes Schönberger <jsch@meta.com>