Minor fixes to Lua includes.

Originally committed to SVN as r1428.

automation/include/unicode.lua

@@ -34,7 +34,7 @@ module("unicode")
 
 -- Return the number of bytes occupied by the character starting at the i'th byte in s
 function charwidth(s, i)
-	local b = s:byte(i)
+	local b = s:byte(i or 1)
 	if not b then
 		--aegisub.debug.out(3, "unicode.charwidth of '%s' @ %d, nil byte\n", s, i)
 		-- FIXME, something in karaskel results in this case, shouldn't happen

automation/include/utils-auto4.lua

@@ -107,13 +107,13 @@ end
 -- Create an alpha override code from a style definition colour code
 function alpha_from_style(scolor)
 	local r, g, b, a = extract_color(scolor)
-	return ass_alpha(a)
+	return ass_alpha(a or 0)
 end
 
 -- Create an colour override code from a style definition colour code
 function color_from_style(scolor)
 	local r, g, b = extract_color(scolor)
-	return ass_color(r, g, b)
+	return ass_color(r or 0, g or 0, b or 0)
 end
 
 -- Converts HSV (Hue, Saturation, Value)  to RGB