Lake panics when creating new project with a numeric name

Running lake new 1234 gives me this panic:

PANIC at Lean.modToFilePath.go Lean.Util.Path:40:20: ill-formed import
backtrace:
0   libleanshared.dylib                 0x0000000113a82728 lean_panic + 268
1   libleanshared.dylib                 0x0000000113a8292c lean_panic_fn + 32
2   libleanshared.dylib                 0x000000011358c574 l_Lean_modToFilePath + 20
3   libLake_shared.dylib                0x0000000105a0e32c l_Lake_initPkg___lambda__6 + 516
4   libLake_shared.dylib                0x0000000105a11b60 l_Lake_initPkg + 556
5   libLake_shared.dylib                0x0000000105a70734 l_Lake_lake_new___lambda__3 + 192
6   libLake_shared.dylib                0x0000000105a7381c l_Lake_lake_new___lambda__3___boxed + 96
7   libleanshared.dylib                 0x0000000113a91674 lean_apply_3 + 960
8   libleanshared.dylib                 0x0000000113a8f9a0 lean_apply_2 + 840
9   libLake_shared.dylib                0x0000000105a4bae8 l_Lake_noArgsRem___rarg + 72
10  libLake_shared.dylib                0x0000000105aecdb0 l_Lake_cli + 580
11  lake                                0x0000000104a84734 _lean_main + 20
12  lake                                0x0000000104a849a0 main + 204
13  dyld                                0x00000001812f8274 start + 2840

Adding a letter to the front of the name prevents the panic.

Start by reproducing the failure with lake new 1234, then compare it with a project name beginning with a letter. Trace the lake new command from its CLI entry point to the project initialization step shown in the panic. Done means numeric project names are handled without a panic and a new project is created.