fix: report an error whe running site:create nameflag is invalid

[Lxxyx]

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Summary

Fixes #4503

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📊 Benchmark results

Comparing with 9e1e55ba4215cab829def3b6793dc2c4ded1dffe

Package size: 222 MB

(no change)

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└───┴──┴────┴──┴────┴──┴────┴──┴────┴──┴────┴──┴────┴──┴────┴──┴────┴──┴────┴──┴────┴──┴────┴──┴────┴──┴──>
    T-12    T-11    T-10    T-9     T-8     T-7     T-6     T-5     T-4     T-3     T-2     T-1      T    

Legend

• T-30 (f02d08e2f86064322547b416dec51ea1d16987fa): 228 MB
• T-29 (64e48dcd3440e137fb9d6d88f4bc1473878af304): 228 MB
• T-28 (7c209cbd0bb6480a0f09444ce49c64eb6711f5da): 228 MB
• T-27 (f362ec752e805323ae26c3c633d7f5920b88498b): 228 MB
• T-26 (585d91e597420bd40d6240f2f02c9623ba6bd99c): 228 MB
• T-25 (91f4ab26087319c1df411cabf108dcee712153d5): 228 MB
• T-24 (868ec26799bc1ae506c4421a579e30cab37266a8): 228 MB
• T-23 (df0c767dc9e97b765f21aa26836b028a784c0d46): 228 MB
• T-22 (0290c4590c1dfb8a7ac485137ab8dacfa0c62927): 228 MB
• T-21 (7337755f16fcd8b8cfa2eff362f2a81d21b484b7): 228 MB
• T-20 (fb72d92c9ba23a5f41ddf7cd9850efd94fecee9d): 228 MB
• T-19 (7317269130ac4017d7d4771ae955f6424ce59e40): 228 MB
• T-18 (3dfa6e522577a7404a7effe0f46ac950a149618a): 228 MB
• T-17 (11b9887e4ef52b9c8cd0097f457d4a7ed08e4f3b): 228 MB
• T-16 (399493929d24bd7d8c2d0ecff165ab7c08b0ceb7): 228 MB
• T-15 (53facba9d475a495e1685b8c30bfec6aa2248dca): 228 MB
• T-14 (d50692225d6364e6598be49d5adb8f76199d500e): 228 MB
• T-13 (dc0615e299afdd9333b892e449021a6be89f0f41): 228 MB
• T-12 (27b484309ee1338451c3b3c0a36e4c6feafed6fd): 222 MB
• T-11 (1e83238ec549c7eaa6eb79ae6a413f85e4b09d5d): 222 MB
• T-10 (ea87d4508e8fcd9e387f8f3d04256f4b64b3cffa): 222 MB
• T-9 (d00841dd913ed6765f1098820b1bd266541edbf1): 222 MB
• T-8 (060c2057723e056030f816ef93b3a8619f83d520): 222 MB
• T-7 (d2d7665979769b4dde34513d9c7df5b7c37d54cc): 222 MB
• T-6 (55df50052240910c4d065634380ba683f600b815): 222 MB
• T-5 (e1b911f9c78e7a49fff90f0d48142bda90469526): 222 MB
• T-4 (58732a298352d8ca5e3766f1076e03a94282a0d5): 222 MB
• T-3 (ddeec5ea06007d8f2ea201fa744b495be1e78216): 222 MB
• T-2 (ec1a05eaa567db80ad84da9364b5be5ac7c082b0): 222 MB
• T-1 (9e1e55ba4215cab829def3b6793dc2c4ded1dffe): 222 MB
• T (current commit): 222 MB