patch 8.2.1862: vim9: memory leak when compiling lambda fails

Problem:    vim9: memory leak when compiling lambda fails.
Solution:   Call clear_evalarg().

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1862,
 /**/
     1861,
 /**/

src/vim9compile.c

@@ -2692,7 +2692,10 @@ compile_lambda(char_u **arg, cctx_T *cctx)
 
     // Get the funcref in "rettv".
     if (get_lambda_tv(arg, &rettv, &evalarg) != OK)
+    {
+	clear_evalarg(&evalarg, NULL);
 	return FAIL;
+    }
 
     ufunc = rettv.vval.v_partial->pt_func;
     ++ufunc->uf_refcount;