Fix useSearch ssr regression

[molefrog]

Fixes #550 - resolves SSR regression where useSearch() crashes in Node.js environments and ensures proper hydration when client renders <Router> without SSR props.

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[github-actions]

size-limit report 📦

Path	Size
packages/wouter/src/index.js	2.19 KB (+0.14% 🔺)
packages/wouter/src/use-browser-location.js	523 B (0%)
packages/wouter/src/memory-location.js	799 B (0%)
packages/wouter/src/use-hash-location.js	720 B (0%)
packages/wouter-preact/src/index.js	2.09 KB (0%)
packages/wouter-preact/src/use-browser-location.js	460 B (0%)
packages/wouter-preact/src/use-hash-location.js	646 B (0%)
packages/wouter-preact/src/memory-location.js	721 B (0%)