Fix stack buffer overrun when weightTotal == 0

If `weightTotal == 0`, then `BIT_highbit32(weightTotal)` is
undefined behavior in the case that it calls `__builtin_clz()`.
If `tableLog == HUF_TABLELOG_ABSOLUTEMAX` then we will access one
byte beyond the end of the buffer.

lib/legacy/zstd_v01.c

@@ -1008,6 +1008,7 @@ static size_t HUF_readDTable (U16* DTable, const void* src, size_t srcSize)
         rankVal[huffWeight[n]]++;
         weightTotal += (1 << huffWeight[n]) >> 1;
     }
+    if (weightTotal == 0) return (size_t)-FSE_ERROR_corruptionDetected;
 
     /* get last non-null symbol weight (implied, total must be 2^n) */
     maxBits = FSE_highbit32(weightTotal) + 1;