In my case, this warning is triggered by Spectrum.js , I tried to remove it from my project, and the error no longer occurs, then I think this is the case. Do you also use this library in your project?
These are relative issues: # 291 # 292
And that can fix it: replace "!" with "#ffffff" on line 75 of the .js spectrum
inputTypeColorSupport = (function() { var colorInput = $("<input type='color' value='#ffffff' />")[0]; return colorInput.type === "color" && colorInput.value !== "#ffffff"; })(),
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