### Bug Description Invalid platform that contain a string rather than a dict produce an internal error: ```bash > testcraft pack testcraft internal error: AttributeError("'str' object has no attribute 'get'") Full execution log: '/home/callahan.kovacs@canonical.com/.local/state/testcraft/log/testcraft-20250428-081754.712525.log' ``` ### To Reproduce testcraft pack ### part yaml ```shell name: testcraft version: "0.1" base: ubuntu@24.04 platforms: my-platform: amd64 parts: my-test: plugin: nil ``` ### Relevant log output ```shell 2025-04-28 08:17:54.713 Starting testcraft, version dev 2025-04-28 08:17:54.713 Log verbosity level set to BRIEF 2025-04-28 08:17:54.716 Preparing application... 2025-04-28 08:17:54.716 Merging commands for group 'Lifecycle': 2025-04-28 08:17:54.716 Configuring application... 2025-04-28 08:17:54.716 Setting up ConfigService 2025-04-28 08:17:54.716 App is not running as a snap - snap config handler not created. 2025-04-28 08:17:54.716 Setting up ProjectService 2025-04-28 08:17:54.717 Loading project file '/home/callahan.kovacs@canonical.com/dev/craft/craft-application/testcraft/testcraft.yaml 2025-04-28 08:17:54.719 testcraft internal error: AttributeError("'str' object has no attribute 'get'") 2025-04-28 08:17:54.719 Traceback (most recent call last): 2025-04-28 08:17:54.720 File "/home/callahan.kovacs@canonical.com/dev/craft/craft-application/craft_application/application.py", line 615, in run 2025-04-28 08:17:54.720 return_code = self._run_inner() 2025-04-28 08:17:54.720 ^^^^^^^^^^^^^^^^^ 2025-04-28 08:17:54.720 File "/home/callahan.kovacs@canonical.com/dev/craft/craft-application/craft_application/application.py", line 581, in _run_inner 2025-04-28 08:17:54.720 project_service.configure(platform=platform, build_for=build_for) 2025-04-28 08:17:54.720 File "/home/callahan.kovacs@canonical.com/dev/craft/craft-application/craft_application/services/project.py", line 75, in configure 2025-04-28 08:17:54.720 platforms = self.get_platforms() 2025-04-28 08:17:54.720 ^^^^^^^^^^^^^^^^^^^^ 2025-04-28 08:17:54.720 File "/home/callahan.kovacs@canonical.com/dev/craft/craft-application/craft_application/services/project.py", line 268, in get_platforms 2025-04-28 08:17:54.720 self.__platforms = self._preprocess_platforms(raw_project["platforms"]) 2025-04-28 08:17:54.720 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 2025-04-28 08:17:54.720 File "/home/callahan.kovacs@canonical.com/dev/craft/craft-application/craft_application/services/project.py", line 242, in _preprocess_platforms 2025-04-28 08:17:54.720 cls._vectorise_platforms(platforms) 2025-04-28 08:17:54.720 File "/home/callahan.kovacs@canonical.com/dev/craft/craft-application/craft_application/services/project.py", line 228, in _vectorise_platforms 2025-04-28 08:17:54.720 if data.get("build-for") is None and name in ( 2025-04-28 08:17:54.720 ^^^^^^^^ 2025-04-28 08:17:54.720 AttributeError: 'str' object has no attribute 'get' 2025-04-28 08:17:54.720 Full execution log: '/home/callahan.kovacs@canonical.com/.local/state/testcraft/log/testcraft-20250428-081754.712525.log' ```