Fix use after move described in ATLASRECTS-5738

In my previous work to migrate the GlobalChi2Fitter to smart pointers, I introduced a minor bug-prone bit of code where a smart pointer may be used after being moved. While this has not been disastrous, it is still erroneous behaviour that clang-tidy picks up on, as described in ATLASRECTS-5738. This commit resolves the issue by keeping a non-unique observer pointer to the object, and using that instead of the unique handle which may be moved. This is mostly a quick fix, the method containing this code is extremely complex and needs some refactoring.

Closes ATLASRECTS-5738.

added bugfix label

WARNING: big files (>100K) are found in the changeset

296K in file Tracking/TrkFitter/TrkGlobalChi2Fitter/src/GlobalChi2Fitter.cxx

This merge request affects 1 file:

• Tracking/TrkFitter/TrkGlobalChi2Fitter/src/GlobalChi2Fitter.cxx

Adding @amorley as watcher

added Tracking master review-pending-level-1 labels

CI Result SUCCESS (hash cfae1d2d)

	Athena	AthSimulation	AthGeneration	AnalysisBase
externals
cmake
make
required tests
optional tests

Full details available on this CI monitor view
Athena: number of compilation errors 0, warnings 0
AthSimulation: number of compilation errors 0, warnings 0
AthGeneration: number of compilation errors 0, warnings 0
AnalysisBase: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 23509]

added review-approved label and removed review-pending-level-1 label

mentioned in commit 112aa27f

merged

added sweep:ignore label