Restrict hex string generation to non-negative values.

It turns out the specific generator I use doesn't support signed
integers, which is OK, since I only ever plug unsigned integers into it.
Updated the function argument type to reflect that.

src/backend/helpers/helpers.cpp

@@ -92,7 +92,7 @@ namespace loot {
     }
 
     //Converts an integer to a hex string using BOOST's Spirit.Karma, which is apparently a lot faster than a stringstream conversion...
-    std::string IntToHexString(const int n) {
+    std::string IntToHexString(const uint32_t n) {
         string out;
         back_insert_iterator<string> sink(out);
         karma::generate(sink, karma::upper[karma::hex], n);

src/backend/helpers/helpers.h

@@ -33,8 +33,8 @@ namespace loot {
     //Calculate the CRC of the given file for comparison purposes.
     uint32_t GetCrc32(const boost::filesystem::path& filename);
 
-    //Converts an integer to a hex string using BOOST's Spirit.Karma. Faster than a stringstream conversion.
-    std::string IntToHexString(const int n);
+    //Converts an unsigned 32-bit integer to a hex string using BOOST's Spirit.Karma. Faster than a stringstream conversion.
+    std::string IntToHexString(const uint32_t n);
 
 #ifdef _WIN32
     //Get registry subkey value string.

src/tests/backend/helpers/test_helpers.h

@@ -39,9 +39,8 @@ TEST_F(GetCrc32, ValidFile) {
     EXPECT_EQ(0x0B5B7B90, loot::GetCrc32(dataPath / "Blank.esp"));
 }
 
-TEST(IntToHexString, PositiveNegativeZeroValues) {
+TEST(IntToHexString, PositiveAndZeroValues) {
     EXPECT_EQ("14", loot::IntToHexString(20));
-    EXPECT_EQ("-14", loot::IntToHexString(-20));
     EXPECT_EQ("0", loot::IntToHexString(0));
 }