algo: fix possible index out of bounds

alib2algo/src/string/properties/BorderArray.h

@@ -24,7 +24,9 @@ ext::vector<size_t> BorderArray::construct(const string::LinearString < SymbolTy
 	ext::vector<size_t> res(w.size() + 1);
 	res[0] = -1;
-	res[1] = 0;
+	if ( w.size ( ) > 0 )
+		res[1] = 0;
+
 	for(size_t i = 1; i < w.size(); i++) {
 		size_t b = res[i];
 		while (b > 0 && w[i] != w[b])