Fix all uninitialized variable warnings (C26495)

Source/UnitTests/Common/x64EmitterTest.cpp

@@ -163,8 +163,8 @@ protected:
 
   std::unique_ptr<X64CodeBlock> emitter;
   std::unique_ptr<disassembler> disasm;
-  u8* code_buffer;
-  u8* code_buffer_end;
+  u8* code_buffer = nullptr;
+  u8* code_buffer_end = nullptr;
 };
 
 #define TEST_INSTR_NO_OPERANDS(Name, ExpectedDisasm)                                               \

Source/UnitTests/Core/MMIOTest.cpp

@@ -67,7 +67,7 @@ class MappingTest : public testing::Test
 protected:
   virtual void SetUp() override { m_mapping = new MMIO::Mapping(); }
   virtual void TearDown() override { delete m_mapping; }
-  MMIO::Mapping* m_mapping;
+  MMIO::Mapping* m_mapping = nullptr;
 };
 
 TEST_F(MappingTest, ReadConstant)

Source/UnitTests/Core/PageFaultTest.cpp

@@ -43,7 +43,7 @@ public:
     return true;
   }
 
-  void* m_data;
+  void* m_data = nullptr;
   std::chrono::time_point<std::chrono::high_resolution_clock> m_pre_unprotect_time,
       m_post_unprotect_time;
 };