fix(shared): fix merge empty object is not work

[janryWang]

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What have you changed?

Fixed #2837

[github-actions]

Size Change: +3 B (0%)

Total Size: 496 kB

Filename	Size	Change
packages/shared/dist/formily.shared.umd.development.js	7.2 kB	+4 B (0%)
packages/shared/dist/formily.shared.umd.production.js	4.17 kB	-1 B (0%)

ℹ️ View Unchanged

Filename	Size
packages/antd/dist/formily.antd.umd.development.js	67.5 kB
packages/antd/dist/formily.antd.umd.production.js	38.7 kB
packages/core/dist/formily.core.umd.development.js	19.5 kB
packages/core/dist/formily.core.umd.production.js	13.2 kB
packages/element/dist/formily.element.umd.development.js	62.8 kB
packages/element/dist/formily.element.umd.production.js	36.5 kB
packages/grid/dist/formily.grid.umd.development.js	9.02 kB
packages/grid/dist/formily.grid.umd.production.js	6.08 kB
packages/json-schema/dist/formily.json-schema.umd.development.js	6.88 kB
packages/json-schema/dist/formily.json-schema.umd.production.js	4.35 kB
packages/next/dist/formily.next.umd.development.js	74.1 kB
packages/next/dist/formily.next.umd.production.js	43.7 kB
packages/path/dist/formily.path.umd.development.js	11 kB
packages/path/dist/formily.path.umd.production.js	7.58 kB
packages/react/dist/formily.react.umd.development.js	11.4 kB
packages/react/dist/formily.react.umd.production.js	7.09 kB
packages/reactive-react/dist/formily.reactive-react.umd.development.js	3.61 kB
packages/reactive-react/dist/formily.reactive-react.umd.production.js	2.25 kB
packages/reactive-vue/dist/formily.reactive-vue.umd.development.js	2.92 kB
packages/reactive-vue/dist/formily.reactive-vue.umd.production.js	1.83 kB
packages/reactive/dist/formily.reactive.umd.development.js	9.3 kB
packages/reactive/dist/formily.reactive.umd.production.js	5.21 kB
packages/validator/dist/formily.validator.umd.development.js	8.42 kB
packages/validator/dist/formily.validator.umd.production.js	6.25 kB
packages/vue/dist/formily.vue.umd.development.js	16.1 kB
packages/vue/dist/formily.vue.umd.production.js	9.64 kB

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[codecov]

Codecov Report

Merging #2841 (29c6a1f) into formily_next (127e0c7) will not change coverage.
The diff coverage is 100.00%.

@@              Coverage Diff              @@
##           formily_next    #2841   +/-   ##
=============================================
  Coverage         95.97%   95.97%           
=============================================
  Files               147      147           
  Lines              6328     6328           
  Branches           1699     1699           
=============================================
  Hits               6073     6073           
  Misses              255      255           

Impacted Files	Coverage Δ
packages/shared/src/merge.ts	98.73% <100.00%> (ø)

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