patch 8.0.1041: bogus characters when indenting during visual-block append

Problem:    Bogus characters appear when indenting kicks in while doing a
            visual-block append.
Solution:   Recompute when indenting is done. (Christian Brabandt)

src/screen.c

@@ -3463,7 +3463,7 @@ win_line(
     {
 	/* For checking first word with a capital skip white space. */
 	if (cap_col == 0)
-	    cap_col = (int)(skipwhite(line) - line);
+	    cap_col = getwhitecols(line);
 
 	/* To be able to spell-check over line boundaries copy the end of the
 	 * current line into nextline[].  Above the start of the next line was