Fix OOB read in inflate_kernel (#15309)

Issue #15216

Avoids an OOB read; the read was not causing bugs as the read data was never used.

Addresses the memcheck part of #15216

Authors:
  - Vukasin Milovanovic (https://github.com/vuule)

Approvers:
  - Bradley Dice (https://github.com/bdice)
  - Muhammad Haseeb (https://github.com/mhaseeb123)

URL: #15309

cpp/src/io/comp/gpuinflate.cu

@@ -804,8 +804,7 @@ __device__ void process_symbols(inflate_state_s* s, int t)
       dist   = symbol >> 16;
       for (int i = t; i < len; i += 32) {
         uint8_t const* src = out + ((i >= dist) ? (i % dist) : i) - dist;
-        uint8_t b          = (src < outbase) ? 0 : *src;
-        if (out + i < outend) { out[i] = b; }
+        if (out + i < outend and src >= outbase) { out[i] = *src; }
       }
       out += len;
       pos++;