[GLIB] Initialize FILE* attributes to nullptr in CGroupMemoryController

https://bugs.webkit.org/show_bug.cgi?id=259185

Reviewed by Carlos Alberto Lopez Perez.

... since the CGroupMemoryController FILE* attributes are not inmediatelly
initialized during the construction but after the creation when
setMemoryControllerPath() is called.

* Source/WebKit/UIProcess/linux/MemoryPressureMonitor.h:

Canonical link: https://commits.webkit.org/266031@main

Source/WebKit/UIProcess/linux/MemoryPressureMonitor.h

@@ -67,15 +67,15 @@ class CGroupMemoryController {
 private:
     CString m_cgroupMemoryControllerPath;
 
-    FILE* m_cgroupMemoryMemswLimitInBytesFile;
-    FILE* m_cgroupMemoryMemswUsageInBytesFile;
-    FILE* m_cgroupMemoryLimitInBytesFile;
-    FILE* m_cgroupMemoryUsageInBytesFile;
-
-    FILE* m_cgroupV2MemoryMemswMaxFile;
-    FILE* m_cgroupV2MemoryMaxFile;
-    FILE* m_cgroupV2MemoryHighFile;
-    FILE* m_cgroupV2MemoryCurrentFile;
+    FILE* m_cgroupMemoryMemswLimitInBytesFile { nullptr };
+    FILE* m_cgroupMemoryMemswUsageInBytesFile { nullptr };
+    FILE* m_cgroupMemoryLimitInBytesFile { nullptr };
+    FILE* m_cgroupMemoryUsageInBytesFile { nullptr };
+
+    FILE* m_cgroupV2MemoryMemswMaxFile { nullptr };
+    FILE* m_cgroupV2MemoryMaxFile { nullptr };
+    FILE* m_cgroupV2MemoryHighFile { nullptr };
+    FILE* m_cgroupV2MemoryCurrentFile { nullptr };
 
     void disposeMemoryController();
     size_t getCgroupFileValue(FILE*);