patch 8.2.2978: warning for uninitialized variable

Problem:    Warning for uninitialized variable.
Solution:   Set return value to FAIL.

src/eval.c

@@ -3777,6 +3777,7 @@ call_func_rettv(
 	    if (s == NULL || *s == NUL)
 	    {
 		emsg(_(e_empty_function_name));
+		ret = FAIL;
 		goto theend;
 	    }
 	}

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2978,
 /**/
     2977,
 /**/