meson: make version numbers ints and fix int/string comparison

WARNING: Trying to compare values of different types (str, int).
The result of this is undefined and will become a hard error
in a future Meson release.
diff --git a/meson.build b/meson.build
index 63b0cd3..d4f05aa 100644
--- a/meson.build
+++ b/meson.build
@@ -6,11 +6,11 @@
 
 gst_version = meson.project_version()
 version_arr = gst_version.split('.')
-gst_version_major = version_arr[0]
-gst_version_minor = version_arr[1]
-gst_version_micro = version_arr[2]
-if version_arr.length() == 4
-  gst_version_nano = version_arr[3]
+gst_version_major = version_arr[0].to_int()
+gst_version_minor = version_arr[1].to_int()
+gst_version_micro = version_arr[2].to_int()
+ if version_arr.length() == 4
+  gst_version_nano = version_arr[3].to_int()
 else
   gst_version_nano = 0
 endif