patch 9.0.0116: virtual text not displayed if 'signcolumn' is "yes"

Problem:    Virtual text not displayed if 'signcolumn' is "yes".
Solution:   Set c_extra and c_final to NUL.

src/drawline.c

@@ -1524,6 +1524,8 @@ win_line(
 			if (p != NULL)
 			{
 			    p_extra = p;
+			    c_extra = NUL;
+			    c_final = NUL;
 			    n_extra = (int)STRLEN(p);
 			    extra_attr = used_attr;
 			    n_attr = n_extra;

src/testdir/dumps/Test_prop_inserts_text_2.dump

@@ -0,0 +1,6 @@
+| +0#0000e05#a8a8a8255@1|i+0#0000000#ffffff0|n|s|e|r|t| |s|o|m|e| |t|e|x|t| |S+0#ffffff16#e000002|O|M|E| |h+0#0000000#ffffff0|e|r|e| |a|n|d| |o|t|h|e|r| |t|e|x|t| |O+0&#ffff4012|T|H|E|R| |t+0&#ffffff0|h|e|r|e| |a|n|d| 
+| +0#0000e05#a8a8a8255@1|s+0#0000000#ffffff0|o|m|e| |m|o|r|e| |t|e|x|t| |a|f|t|e|r| |M+0&#5fd7ff255|O|R|E| |w+0&#ffffff0|r|a|p@1|i|n|g> @23
+|~+0#4040ff13&| @58
+|~| @58
+|~| @58
+| +0#0000000&@41|1|,|7@1|-|9|3| @6|A|l@1| 

src/testdir/test_textprop.vim

@@ -2204,7 +2204,10 @@ func Test_prop_inserts_text()
   END
   call writefile(lines, 'XscriptPropsWithText')
   let buf = RunVimInTerminal('-S XscriptPropsWithText', #{rows: 6, cols: 60})
-  call VerifyScreenDump(buf, 'Test_prop_inserts_text', {})
+  call VerifyScreenDump(buf, 'Test_prop_inserts_text_1', {})
+
+  call term_sendkeys(buf, ":set signcolumn=yes\<CR>")
+  call VerifyScreenDump(buf, 'Test_prop_inserts_text_2', {})
 
   call StopVimInTerminal(buf)
   call delete('XscriptPropsWithText')

src/version.c

@@ -735,6 +735,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    116,
 /**/
     115,
 /**/