Strip non-ASCII chars from signs when WB-saving

This BtS bug has been reported here:
https://forums.civfanatics.com/threads/ctd-python-error.684770/

Had likely resulted in an unusable WB save file or none. [advc.001]

Assets/Python/pyWB/CvWBDesc.py

@@ -1473,7 +1473,10 @@ def write(self, f, sign):
 		f.write("\tplotX=%d\n" %(sign.getPlot().getX(),))
 		f.write("\tplotY=%d\n" %(sign.getPlot().getY(),))
 		f.write("\tplayerType=%d\n" %(sign.getPlayerType(),))
-		f.write("\tcaption=%s\n" %(sign.getCaption(),))
+		uCaption = sign.getCaption()
+		# advc.001: Strip non-ascii
+		uCaption = uCaption.encode('ascii', 'ignore').decode()
+		f.write("\tcaption=%s\n" %(uCaption,))
 		f.write("EndSign\n")
 
 	def read(self, f):