Prevent the hashing function being called when capacity is zero #7439

Job	Run time
Build LPython to WASM	5m 52s
Build LPython to WASM	5m 52s
Build Jupyter Kernel	3m 21s
Build Jupyter Kernel	3m 20s
Test CPython Interop (@pythoncall)	1m 28s
Test CPython Interop (@pythoncall)	1m 28s
LPython CI (3.10, ubuntu-latest)	8m 38s
LPython CI (3.10, ubuntu-latest)	8m 38s
LPython CI (3.10, macos-latest)	8m 9s
LPython CI (3.10, macos-latest)	8m 9s
LPython CI (3.10, windows-2019)	13m 28s
LPython CI (3.10, windows-2019)	13m 28s
Check Debug build	2m 36s
Check Debug build	2m 36s
Run Integration tests with Python 3.9	1m 35s
Run Integration tests with Python 3.9	1m 35s
Check Release build	2m 26s
Check Release build	2m 26s
Run Integration tests with Python 3.10	1m 36s
Run Integration tests with Python 3.10	1m 36s
Run SymPy tests	1m 59s
Run SymPy tests	1m 59s
Run Integration tests with Python 3.11	1m 36s
Run Integration tests with Python 3.11	1m 36s
Test LLVM 10	2m 25s
Test LLVM 10	2m 25s
Run Integration tests with Python 3.12	1m 36s
Run Integration tests with Python 3.12	1m 36s
Test PIP Installable Packages	1m 10s
Test PIP Installable Packages	1m 10s
Test LLVM 15	2m 34s
Test LLVM 15	2m 34s
Test LLVM 16	2m 30s
Test LLVM 16	2m 30s
Upload Tarball	42s
Upload Tarball	42s
	2h 7m 21s

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