[ufowrite] setVersionMajor function does not handle leading zero correctly

[tamcy]

The setVersionMajor function in ufowrite.c is supposed to copy the major version number from a version string to a destination string, skipping leading zeros. However, when the major version is zero (e.g. 0.500), nothing will be copied and the destination string (dst) ends up being empty.

I encountered the issue that causes an empty value (nothing) being written to the versionMajor property of fontinfo.plist when exporting to ufo format with tx, which isn't valid:

	<key>versionMajor</key>
	<integer></integer>

I believe it could be fixed by something like this: tamcy@a36fc9e

diff --git "a/c/shared/source/ufowrite/ufowrite.c" "b/c/shared/source/ufowrite/ufowrite.c"
index 64ee9e63..3703837a 100644
--- "a/c/shared/source/ufowrite/ufowrite.c"
+++ "b/c/shared/source/ufowrite/ufowrite.c"
@@ -875,6 +875,8 @@ static void setVersionMajor(char *dst, char *version) {
             seenNonZero = 1;
         }
     }
+    if (!seenNonZero)
+        *dst++ = '0';
     *dst = 0x00;
 }

Indeed this is what is happening in setVersionMinor. I am not familar with this repo good enough to contribute a test case so I'm not submitting a pull request.