[msbuild] Fix the PropertyListEditor task to correctly handle two input files. Fixes #24091.

[rolfbjarne]

Fix the PropertyListEditor task to not only check for null input, but also
empty empty - this fixes an regression where we changed the default property
value for the task inputs from null to an empty string, and then any null
checks later on would fail.

Fixes #24091.

[vs-mobiletools-engineering-service2]

✅ [CI Build #dc05811] Build passed (Build packages) ✅

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Hash: dc05811f0cf6a33da052a7b71033af3d741d9fc9 [PR build]

[vs-mobiletools-engineering-service2]

✅ [PR Build #dc05811] Build passed (Detect API changes) ✅

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Hash: dc05811f0cf6a33da052a7b71033af3d741d9fc9 [PR build]

[vs-mobiletools-engineering-service2]

✅ API diff for current PR / commit

NET (empty diffs)

• iOS: vsdrops gist ( No breaking changes )
• tvOS: vsdrops gist ( No breaking changes )
• MacCatalyst: vsdrops gist ( No breaking changes )
• macOS: vsdrops gist ( No breaking changes )

✅ API diff vs stable

NET (empty diffs)

• iOS: vsdrops gist ( No breaking changes )
• tvOS: vsdrops gist ( No breaking changes )
• MacCatalyst: vsdrops gist ( No breaking changes )
• macOS: vsdrops gist ( No breaking changes )

ℹ️ Generator diff

Generator Diff: vsdrops (html) vsdrops (raw diff) gist (raw diff) - Please review changes)

Pipeline on Agent
Hash: dc05811f0cf6a33da052a7b71033af3d741d9fc9 [PR build]

[vs-mobiletools-engineering-service2]

✅ [CI Build #dc05811] Build passed (Build macOS tests) ✅

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Hash: dc05811f0cf6a33da052a7b71033af3d741d9fc9 [PR build]

[vs-mobiletools-engineering-service2]

💻 [CI Build #dc05811] Tests on macOS X64 - Mac Sonoma (14) passed 💻

✅ All tests on macOS X64 - Mac Sonoma (14) passed.

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Hash: dc05811f0cf6a33da052a7b71033af3d741d9fc9 [PR build]

[vs-mobiletools-engineering-service2]

💻 [CI Build #dc05811] Tests on macOS M1 - Mac Monterey (12) passed 💻

✅ All tests on macOS M1 - Mac Monterey (12) passed.

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Hash: dc05811f0cf6a33da052a7b71033af3d741d9fc9 [PR build]

[vs-mobiletools-engineering-service2]

💻 [CI Build #dc05811] Tests on macOS M1 - Mac Ventura (13) passed 💻

✅ All tests on macOS M1 - Mac Ventura (13) passed.

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Hash: dc05811f0cf6a33da052a7b71033af3d741d9fc9 [PR build]

[vs-mobiletools-engineering-service2]

💻 [CI Build #dc05811] Tests on macOS arm64 - Mac Tahoe (26) passed 💻

✅ All tests on macOS arm64 - Mac Tahoe (26) passed.

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Hash: dc05811f0cf6a33da052a7b71033af3d741d9fc9 [PR build]

[vs-mobiletools-engineering-service2]

💻 [CI Build #dc05811] Tests on macOS arm64 - Mac Sequoia (15) passed 💻

✅ All tests on macOS arm64 - Mac Sequoia (15) passed.

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Hash: dc05811f0cf6a33da052a7b71033af3d741d9fc9 [PR build]

[vs-mobiletools-engineering-service2]

🚀 [CI Build #dc05811] Test results 🚀

Test results

✅ All tests passed on VSTS: test results.

🎉 All 119 tests passed 🎉

Tests counts

✅ cecil: All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (iOS): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (MacCatalyst): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (macOS): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (Multiple platforms): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (tvOS): All 1 tests passed. Html Report (VSDrops) Download
✅ framework: All 2 tests passed. Html Report (VSDrops) Download
✅ fsharp: All 4 tests passed. Html Report (VSDrops) Download
✅ generator: All 5 tests passed. Html Report (VSDrops) Download
✅ interdependent-binding-projects: All 4 tests passed. Html Report (VSDrops) Download
✅ introspection: All 4 tests passed. Html Report (VSDrops) Download
✅ linker: All 44 tests passed. Html Report (VSDrops) Download
✅ monotouch (iOS): All 8 tests passed. Html Report (VSDrops) Download
✅ monotouch (MacCatalyst): All 15 tests passed. Html Report (VSDrops) Download
✅ monotouch (macOS): All 9 tests passed. Html Report (VSDrops) Download
✅ monotouch (tvOS): All 8 tests passed. Html Report (VSDrops) Download
✅ msbuild: All 2 tests passed. Html Report (VSDrops) Download
✅ windows: All 3 tests passed. Html Report (VSDrops) Download
✅ xcframework: All 4 tests passed. [attempt 3] Html Report (VSDrops) Download
✅ xtro: All 1 tests passed. Html Report (VSDrops) Download

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Hash: dc05811f0cf6a33da052a7b71033af3d741d9fc9 [PR build]