patch 9.0.1083: empty and comment lines in a class cause an error

Problem:    Empty and comment lines in a class cause an error.
Solution:   Skip empty and comment lines. (closes #11734)

src/testdir/test_vim9_class.vim

@@ -131,6 +131,7 @@ def Test_class_basic()
         this.lnum: number
         this.col: number
 
+        # make a nicely formatted string
         def ToString(): string
           return $'({this.lnum}, {this.col})'
         enddef
@@ -155,6 +156,7 @@ def Test_class_member_initializer()
         this.lnum: number = 1
         this.col: number = 1
 
+        # constructor with only the line number
         def new(lnum: number)
           this.lnum = lnum
         enddef

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1083,
 /**/
     1082,
 /**/

src/vim9class.c

@@ -248,6 +248,16 @@ ex_class(exarg_T *eap)
 	    break;
 	char_u *line = skipwhite(theline);
 
+	// Skip empty and comment lines.
+	if (*line == NUL)
+	    continue;
+	if (*line == '#')
+	{
+	    if (vim9_bad_comment(line))
+		break;
+	    continue;
+	}
+
 	char_u *p = line;
 	if (checkforcmd(&p, "endclass", 4))
 	{