patch 9.0.1637: compiler warning for uninitialized variable

Problem:    Compiler warning for uninitialized variable.
Solution:   Move the variable to an inner block and initialize it. (Christian
            Brabandt, closes #12549)
diff --git a/src/version.c b/src/version.c
index 6a70e21..a91e6fb 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1637,
+/**/
     1636,
 /**/
     1635,