seq: Trim whitespaces, then try to remove +

Otherwise, `seq` crashes with ` 0xee.` as input.

Author: drinkcat

src/uu/seq/src/numberparse.rs

@@ -27,9 +27,10 @@ pub enum ParseNumberError {
 // need to be too careful.
 fn compute_num_digits(input: &str, ebd: ExtendedBigDecimal) -> PreciseNumber {
     let input = input.to_lowercase();
+    let input = input.trim_start();
 
     // Leading + is ignored for this.
-    let input = input.trim_start().strip_prefix('+').unwrap_or(&input);
+    let input = input.strip_prefix('+').unwrap_or(&input);
 
     // Integral digits for any hex number is ill-defined (0 is fine as an output)
     // Fractional digits for an floating hex number is ill-defined, return None