patch 8.0.0526: Coverity complains about possible negative value

Problem:    Coverity complains about possible negative value.
Solution:   Check return value of ftell() not to be negative.
diff --git a/src/version.c b/src/version.c
index ba3aefc..436b2a1 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    526,
+/**/
     525,
 /**/
     524,