Failure of consolidate plugin

### Description

Running scancode with consolidate plugin failed on zig source tree.

### How To Reproduce
```
% wget https://ziglang.org/download/0.9.1/zig-0.9.1.tar.xz
% tar xf zig-0.9.1.tar.xz
% cd zig-0.9.1
% scancode -n 6 --license --copyright --license-text --consolidate --debian ~/debian-copyright .
Setup plugins...
Collect file inventory...
Scan files for: licenses, copyrights with 6 process(es)...
[####################] 28456
/home/hastings/.local/lib/python3.9/site-packages/scancode/cli.py:1077: ConsolidatorPluginDeprecationWarning: The --consolidate option will be de
precated in a future version of scancode-toolkit.
plugin.process_codebase(codebase, **kwargs)
ERROR: failed to run post-scan plugin: consolidate:
Traceback (most recent call last):
File "/home/hastings/.local/lib/python3.9/site-packages/scancode/cli.py", line 1077, in run_codebase_plugins
plugin.process_codebase(codebase, **kwargs)
File "/home/hastings/.local/lib/python3.9/site-packages/summarycode/plugin_consolidate.py", line 176, in process_codebase
consolidations.extend(get_holders_consolidated_components(codebase))
File "/home/hastings/.local/lib/python3.9/site-packages/summarycode/plugin_consolidate.py", line 399, in get_holders_consolidated_components
for c in create_consolidated_components(resource, codebase, holder):
File "/home/hastings/.local/lib/python3.9/site-packages/summarycode/plugin_consolidate.py", line 413, in create_consolidated_components
if not (normalized_holder.key == holder_key):
AttributeError: 'dict' object has no attribute 'key'

Scanning done.
Some files failed to scan properly:
ERROR: failed to run post-scan plugin: consolidate:
Traceback (most recent call last):
File "/home/hastings/.local/lib/python3.9/site-packages/scancode/cli.py", line 1077, in run_codebase_plugins
plugin.process_codebase(codebase, **kwargs)
File "/home/hastings/.local/lib/python3.9/site-packages/summarycode/plugin_consolidate.py", line 176, in process_codebase
consolidations.extend(get_holders_consolidated_components(codebase))
File "/home/hastings/.local/lib/python3.9/site-packages/summarycode/plugin_consolidate.py", line 399, in get_holders_consolidated_components
for c in create_consolidated_components(resource, codebase, holder):
File "/home/hastings/.local/lib/python3.9/site-packages/summarycode/plugin_consolidate.py", line 413, in create_consolidated_components
if not (normalized_holder.key == holder_key):
AttributeError: 'dict' object has no attribute 'key'
Summary: licenses, copyrights with 6 process(es)
Errors count: 1
Scan Speed: 9.98 files/sec.
Initial counts: 15400 resource(s): 14228 file(s) and 1172 directorie(s)
Final counts: 15400 resource(s): 14228 file(s) and 1172 directorie(s)
Timings:
scan_start: 2022-10-24T234607.752111
scan_end: 2022-10-25T001006.418499
setup_scan:licenses: 1.42s
setup: 1.42s
inventory: 2.84s
scan: 1425.52s
post-scan:consolidate: 3.08s
post-scan: 3.08s
output:debian: 3.70s
output: 3.70s
total: 1443.01s
Removing temporary files...done.
scancode -n 6 --license --copyright --license-text --consolidate --debian . 8545.88s user 14.63s system 592% cpu 24:04.62 total
```
### System configuration

* OS: Debian 11
* Installation method: `python3 -m pip install --user scancode-toolkit`
* Scancode version:
```
% scancode --version
ScanCode version: 31.2.1
ScanCode Output Format version: 2.0.0
SPDX License list version: 3.17```