patch 8.2.1324: Vim9: line break after "=" does not work

Problem:    Vim9: line break after "=" does not work.
Solution:   Also allow for NUL after "=". (closes #6549)

src/evalvars.c

@@ -801,13 +801,13 @@ ex_let(exarg_T *eap)
 	    else
 		++expr;
 
-	    if (vim9script && (!VIM_ISWHITE(*argend) || !VIM_ISWHITE(*expr)))
+	    if (vim9script && (!VIM_ISWHITE(*argend)
+						   || !IS_WHITE_OR_NUL(*expr)))
 	    {
 		vim_strncpy(op, expr - len, len);
 		semsg(_(e_white_both), op);
 		i = FAIL;
 	    }
-	    expr = skipwhite(expr);
 
 	    if (eap->skip)
 		++emsg_skip;
@@ -818,6 +818,7 @@ ex_let(exarg_T *eap)
 		evalarg.eval_getline = eap->getline;
 		evalarg.eval_cookie = eap->cookie;
 	    }
+	    expr = skipwhite_and_linebreak(expr, &evalarg);
 	    i = eval0(expr, &rettv, eap, &evalarg);
 	    if (eap->skip)
 		--emsg_skip;

src/testdir/test_vim9_script.vim

@@ -358,6 +358,25 @@ def Test_assignment_var_list()
   assert_equal(['three'], vrem)
 enddef
 
+def Test_assignment_vim9script()
+  let lines =<< trim END
+    vim9script
+    def Func(): list<number>
+      return [1, 2]
+    enddef
+    let var1: number
+    let var2: number
+    [var1, var2] =
+          Func()
+    assert_equal(1, var1)
+    assert_equal(2, var2)
+    let ll =
+          Func()
+    assert_equal([1, 2], ll)
+  END
+  CheckScriptSuccess(lines)
+enddef
+
 def Mess(): string
   v:foldstart = 123
   return 'xxx'

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1324,
 /**/
     1323,
 /**/