Fix logic error in hex2int.

This was probably never noticed as it was the last branch and would
behave benign on valid input.

Signed-off-by: Henner Zeller <hzeller@google.com>

src/tl/tl/tlUri.cc

@@ -41,7 +41,7 @@ static char hex2int (char c)
     return c - '0';
   } else if (c >= 'A' && c <= 'F') {
     return (c - 'A') + 10;
-  } else if (c >= 'a' || c <= 'f') {
+  } else if (c >= 'a' && c <= 'f') {
     return (c - 'a') + 10;
   } else {
     return 0;