patch 8.2.4970: "eval 123" gives an error, "eval 'abc'" does not

Problem:    "eval 123" gives an error, "eval 'abc'" does not.
Solution:   Also give an error when evaluating only a string. (closes #10434)

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4970,
 /**/
     4969,
 /**/