Fix NumberFormatException in SketchTool.loadSketchesFromString for single-k sketches

[rec3141]

Fixes #23.

Summary

TaxServer (the sendsketch.sh server) returns HTTP 400 for every query whose sketch uses a single k-mer length (e.g. a local k=31 sketch server), due to a NumberFormatException in SketchTool.loadSketchesFromString().

Root cause

In current/sketch/SketchTool.java, the K: (k-mer length) header parser in loadSketchesFromString() has a comma branch (dual-k, e.g. K:32,24) and a single-value branch. The single-value branch parsed the full field string s ("K:31") instead of the value substring sub ("31"):

}else if(s.startsWith("K:")){//Kmer length
    if(sub.indexOf(',')>=0){
        String[] subsplit=sub.split(",");
        int x=Integer.parseInt(subsplit[0]);
        int y=Integer.parseInt(subsplit[1]);
        ...
    }else{
        k_sketch=Integer.parseInt(s);   // <-- "K:31" is not an int -> NumberFormatException
        k2_sketch=0;
    }
}

Every other field parser in the same block (H:, BC:, GS:, GK:, …) and the comma branch correctly use sub. Only this single-k branch used s. The two file-reading parsers (loadSketchesFromSketchFile/...File2) were already correct — only loadSketchesFromString (the path that parses incoming sendsketch POST data) was affected.

Fix

-										k_sketch=Integer.parseInt(s);
+										k_sketch=Integer.parseInt(sub);

Reproduction & verification (on current master, v39.91)

Built two tiny per-sequence sketch DBs from a 5-contig FASTA, started TaxServer with each, and queried via sendsketch.sh:

query sketch	unpatched 39.91	patched
single k=31 (K:31)	HTTP 400 / NumberFormatException	✅ returns results
default dual-k (K:32,24)	✅ returns results	✅ returns results

So default dual-k sketches were never affected (they take the comma branch) — which is why public default-k servers never hit this — but any single-k custom server (common for self-hosted GTDB/RefSeq sketch DBs built with k=31) returns 400 on every query. The fix restores single-k servers while leaving the dual-k path unchanged.

Environment

• BBTools master @ v39.91 (also confirmed present in 39.52)
• OpenJDK 11

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