Fix for corner case in shortcut storage that is used by PlumedToHTML #2886

Job	Run time
docker / docker (fedora39)	20m 23s
conda / conda (ubuntu-20.04)	10m 27s
codecheck / codecheck	38m 26s
conda / conda (macos-12)	18m 42s
docker / docker (rocky8)	22m 33s
conda / conda (macos-14)	7m 55s
linux / linux (-doc-mpi-)	41m 6s
mac / macports (macos-12)	7m 23s
linux / linux (-mpi-)	48m 56s
mac / macsimple (macos-12)	8m 31s
linux / linux (-coverage-mpi-)	1h 0m 5s
mac / macports (macos-14)	5m 14s
mac / macports (+allmodules, macos-12)	19m 15s
mac / macsimple (macos-14)	4m 39s
linux / linux (-debug-)	29m 6s
linux / linux (-debug-mpi-)	38m 43s
linux / linux (-intel-)	47m 15s
linux / linux (-pycv-mpi-)	16m 41s
	7h 25m 20s

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