allow the initial setHtml() request to proceed

Qt 5.11 appears to call acceptNavigationRequest() for the initial
page load now.

aqt/webview.py

@@ -68,6 +68,9 @@ class AnkiWebPage(QWebEnginePage):
     def acceptNavigationRequest(self, url, navType, isMainFrame):
         if not isMainFrame:
             return True
+        # data: links generated by setHtml()
+        if url.scheme() == "data":
+            return True
         from aqt import mw
         # ignore href=#
         if url.toString().startswith(mw.serverURL()):