[Figma Bridge] Uncaught exception when exporting: "TypeError: Cannot read properties of undefined (reading 'toUpperCase')"

PLUGIN_4_SOURCE:1 Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'toUpperCase')
    at q (PLUGIN_4_SOURCE:1:372964)
    at pe (PLUGIN_4_SOURCE:1:384192)
    at eval (PLUGIN_4_SOURCE:1:385314)
    at Array.map (<anonymous>)
    at pe (PLUGIN_4_SOURCE:1:385266)
    at eval (PLUGIN_4_SOURCE:1:383621)
    at eval (PLUGIN_4_SOURCE:1:383762)
    at Array.map (<anonymous>)
    at ue (PLUGIN_4_SOURCE:1:383230)
    at eval (PLUGIN_4_SOURCE:1:386756)
q @ PLUGIN_4_SOURCE:1
pe @ PLUGIN_4_SOURCE:1
eval @ PLUGIN_4_SOURCE:1
pe @ PLUGIN_4_SOURCE:1
eval @ PLUGIN_4_SOURCE:1
eval @ PLUGIN_4_SOURCE:1
ue @ PLUGIN_4_SOURCE:1
eval @ PLUGIN_4_SOURCE:1
export-request @ PLUGIN_4_SOURCE:1
figma.ui.onmessage @ PLUGIN_4_SOURCE:1
callFunction @ figma_app.min.js.br:2212
iframeMessageHandler @ figma_app.min.js.br:2901
JSr.toplevelWindowMessageChannel.port2.onmessage @ figma_app.min.js.br:2769
await in JSr.toplevelWindowMessageChannel.port2.onmessage (async)
figma.ui.onmessage @ PLUGIN_4_SOURCE:1
callFunction @ figma_app.min.js.br:2212
iframeMessageHandler @ figma_app.min.js.br:2901
JSr.toplevelWindowMessageChannel.port2.onmessage @ figma_app.min.js.br:2769