[BUG] Error on npm install with workspaces: "Cannot set properties of null (setting 'dev')"

Is there an existing issue for this?

• I have searched the existing issues

Current Behavior

In an npm workspaces project we have a usecase of nested package - in the directory of package "a" we have a directory containing another package "a-inner".
A different package "b" depends on "a-inner"

trying to npm install only package "b": npm install --workspace @npmwsbug/b
results in an error

log lines from npm log:

58 verbose stack TypeError: Cannot set properties of null (setting 'dev')
58 verbose stack     at calcDepFlagsStep (/home/alex/.npm-packages/lib/node_modules/npm/node_modules/@npmcli/arborist/lib/calc-dep-flags.js:34:21)
58 verbose stack     at visit (/home/alex/.npm-packages/lib/node_modules/npm/node_modules/@npmcli/arborist/lib/calc-dep-flags.js:12:20)
58 verbose stack     at visitNode (/home/alex/.npm-packages/lib/node_modules/npm/node_modules/treeverse/lib/depth-descent.js:57:25)
58 verbose stack     at next (/home/alex/.npm-packages/lib/node_modules/npm/node_modules/treeverse/lib/depth-descent.js:44:19)
58 verbose stack     at depth (/home/alex/.npm-packages/lib/node_modules/npm/node_modules/treeverse/lib/depth-descent.js:82:10)
58 verbose stack     at depth (/home/alex/.npm-packages/lib/node_modules/npm/node_modules/treeverse/lib/depth.js:27:12)
58 verbose stack     at calcDepFlags (/home/alex/.npm-packages/lib/node_modules/npm/node_modules/@npmcli/arborist/lib/calc-dep-flags.js:10:15)
58 verbose stack     at Arborist.[copyIdealToActual] (/home/alex/.npm-packages/lib/node_modules/npm/node_modules/@npmcli/arborist/lib/arborist/reify.js:1400:7)
58 verbose stack     at Arborist.reify (/home/alex/.npm-packages/lib/node_modules/npm/node_modules/@npmcli/arborist/lib/arborist/reify.js:153:35)
58 verbose stack     at async Install.install (/home/alex/.npm-packages/lib/node_modules/npm/lib/install.js:170:5)

Expected Behavior

workspace should be installed successfully

Steps To Reproduce

clone following example repo - https://github.com/alexpusch/npm-ws-bug-example
run npm install --workspace @npmwsbug/b

error will appear:
TypeError: Cannot set properties of null (setting 'dev')

Environment

• OS: Ubuntu 20
• Node: 16.9.1
• npm: 8.1.0

Reproduce the failure from npm-ws-bug-example with npm install --workspace @npmwsbug/b, then start at @npmcli/arborist/lib/calc-dep-flags.js:34 and follow the reify entry point shown in the stack trace. Done means the workspace installs successfully without the null-property TypeError.