Empty cells in numeric metadata column causing error with viewing feature-table.qzv

[cherman2]

Bug Description
There is a "SyntaxError: JSON.parse: unexpected character at line 2 column 41185 of the JSON data" in q2-view on the interactive sample detail tab.

I inspected the webpage and found this console error: Query.Deferred exception: JSON.parse: unexpected character at line 2 column 41185 of the JSON data @https://view.qiime2.org/_/tzxmdl1o9jo/597ab77e-f75a-43b9-8726-cfb6d6b00bcb/data/sample-frequency-detail.html:131:21
j@https://view.qiime2.org/_/tzxmdl1o9jo/597ab77e-f75a-43b9-8726-cfb6d6b00bcb/data/q2templateassets/js/jquery-3.2.0.min.js:2:29999
Deferred/then/g/</k<@https://view.qiime2.org/_/tzxmdl1o9jo/597ab77e-f75a-43b9-8726-cfb6d6b00bcb/data/q2templateassets/js/jquery-3.2.0.min.js:2:30313
undefined

I also received the same error on chrome with a different error: Uncaught SyntaxError: Unexpected token 'N', ..."atitude": NaN, "Long"... is not valid JSON. This error ended up being more helpful in pinpointing the reason behind the error.

This error occurs when you summarize a feature table in QIIME2-2022.8 and the qiime2-dev env and view it with qiime2 view, however it does not occur when summarized in 2022.2.

its seems that 2022.8 uses Nan in the sample-frequency-detail.html for blank cells in numeric metadata columns and null in categorical metadata columns while 2022.2 only uses null

2022.8: This a screenshot from my metadata. Weather condition is categorical and Null while Latitude is numeric and Nan.

2022.2: Both are null.

Steps to reproduce the behavior

1. Have metadata that has blank cells in a numeric column
2. activate qiime2-2022.8 env
3. run qiime feature-table summarize with metadata
4. run qiime tools view or drag and drop .qzv into view.qiime2.org
5. click on Interactive Sample Details
6. see error

Expected behavior
The expected behavior is to be able to see the interactive quality plot but instead there is an error.

Computation Environment

• OS: macOS Catalina
• QIIME 2 Release 2022.8 and the most recent qiime2-dev
• Firefox v104.0.1 (64-bit)

Thanks @Oddant1 and @lizgehret for the help debugging this!