patch 9.0.1705: cursor position wrong when clicking on an unprintable char

Problem:  cursor position wrong when clicking on an unprintable char
Solution: Don't update prev_ptr when wlv.n_extra is not zero.

closes: #12664

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: zeertzjq <zeertzjq@outlook.com>
diff --git a/src/drawline.c b/src/drawline.c
index 9d6ee8d..ef9f663 100644
--- a/src/drawline.c
+++ b/src/drawline.c
@@ -1829,10 +1829,10 @@
 
     win_line_start(wp, &wlv, FALSE);
 
+    char_u	*prev_ptr = ptr;
     // Repeat for the whole displayed line.
     for (;;)
     {
-	char_u	*prev_ptr = ptr;
 #if defined(FEAT_CONCEAL) || defined(FEAT_SEARCH_EXTRA)
 	int	has_match_conc = 0;	// match wants to conceal
 #endif
@@ -2261,9 +2261,9 @@
 	    }
 #endif
 
-#ifdef FEAT_SEARCH_EXTRA
 	    if (wlv.n_extra == 0)
 	    {
+#ifdef FEAT_SEARCH_EXTRA
 		// Check for start/end of 'hlsearch' and other matches.
 		// After end, check for start/end of next match.
 		// When another match, have to check for start again.
@@ -2273,15 +2273,16 @@
 				      &match_conc, did_line_attr, lcs_eol_one,
 				      &on_last_col);
 		ptr = line + v;  // "line" may have been changed
-		prev_ptr = ptr;
 
 		// Do not allow a conceal over EOL otherwise EOL will be missed
 		// and bad things happen.
 		if (*ptr == NUL)
 		    has_match_conc = 0;
-	    }
 #endif
 
+		prev_ptr = ptr;
+	    }
+
 #ifdef FEAT_DIFF
 	    if (wlv.diff_hlf != (hlf_T)0)
 	    {