patch 8.2.4990: memory leak when :defcompile fails

Problem:    Memory leak when :defcompile fails.
Solution:   Free fname when returning early.
diff --git a/src/userfunc.c b/src/userfunc.c
index 6eabd8b..bc4bc45 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -5037,6 +5037,7 @@
     }
     if (!ends_excmd2(name, arg))
     {
+	vim_free(fname);
 	emsg(ex_errmsg(e_trailing_characters_str, arg));
 	return NULL;
     }