Replace zero constants with nullptr

Source/Core/Common/Hash.cpp

@@ -427,7 +427,7 @@ u64 GetHash64(const u8* src, u32 len, u32 samples)
 
 u32 StartCRC32()
 {
-  return crc32_z(0L, Z_NULL, 0);
+  return crc32_z(0L, nullptr, 0);
 }
 
 u32 UpdateCRC32(u32 crc, const u8* data, size_t len)

Source/Core/Common/MemArenaUnix.cpp

@@ -149,8 +149,8 @@ void* LazyMemoryRegion::Create(size_t size)
   if (size == 0)
     return nullptr;
 
-  void* memory =
-      mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0);
+  void* memory = mmap(nullptr, size, PROT_READ | PROT_WRITE,
+                      MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0);
   if (memory == MAP_FAILED)
   {
     NOTICE_LOG_FMT(MEMMAP, "Memory allocation of {} bytes failed.", size);

Source/Core/Common/TimeUtil.cpp

@@ -17,7 +17,7 @@ std::optional<std::tm> LocalTime(std::time_t time)
 #ifdef _MSC_VER
   if (localtime_s(&local_time, &time) != 0)
 #else
-  if (localtime_r(&time, &local_time) == NULL)
+  if (localtime_r(&time, &local_time) == nullptr)
 #endif
   {
     ERROR_LOG_FMT(COMMON, "Failed to convert time to local time: {}", std::strerror(errno));

Source/Core/Core/PowerPC/JitCommon/JitCache.h

@@ -231,7 +231,7 @@ private:
   // It is used by the assembly dispatcher to quickly
   // know where to jump based on pc and msr bits.
   Common::LazyMemoryRegion m_entry_points_arena;
-  u8** m_entry_points_ptr = 0;
+  u8** m_entry_points_ptr = nullptr;
 
   // An alternative for the above but without a shm segment
   // in case the shm memory region couldn't be allocated.

Source/Core/DolphinQt/Debugger/BreakpointWidget.cpp

@@ -78,7 +78,7 @@ private:
     opt.decorationSize = QSize(0, 0);
 
     // Default draw command for paint.
-    QApplication::style()->drawControl(QStyle::CE_ItemViewItem, &opt, painter, 0);
+    QApplication::style()->drawControl(QStyle::CE_ItemViewItem, &opt, painter, nullptr);
 
     // Draw pixmap at the center of the tablewidget cell
     QPixmap pix = qvariant_cast<QPixmap>(index.data(Qt::DecorationRole));

Source/Core/VideoCommon/PerformanceMetrics.cpp

@@ -191,7 +191,7 @@ void PerformanceMetrics::DrawImGuiStats(const float backbuffer_scale)
   if (g_ActiveConfig.bShowGraphs)
   {
     // A font size of 13 is small enough to keep the tick numbers from overlapping too much.
-    ImGui::PushFont(NULL, 13.0f);
+    ImGui::PushFont(nullptr, 13.0f);
     ImGui::PushStyleColor(ImGuiCol_ResizeGrip, 0);
     const auto graph_flags = ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoSavedSettings |
                              ImGuiWindowFlags_NoScrollbar | ImGuiWindowFlags_NoNav | movable_flag |