id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,active_lock_reason,draft,pull_request,body,reactions,performed_via_github_app,state_reason,repo,type
1445870847,PR_kwDOAMm_X85CuWCd,7281,Use a default value for constant dimensions,14371165,closed,0,,,1,2022-11-11T18:41:16Z,2022-11-20T09:59:38Z,2022-11-20T09:59:38Z,MEMBER,,0,pydata/xarray/pulls/7281,"* default markersize values of widths are 18 to 72.
* plt.scatter default markersize is 36.
* plt.plot default linewidth is 6.

With main we get 18 for constant arrays, but 36 if markersize was undefined. This seems a bit inconsistent to me. 
This PR adds a default value instead for constant arrays

Follow up to #7272.","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/7281/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,pull