Crash report generation can crash when `StackTraceElement.getFileName()` is null

Minecraft's crash report generation can throw a secondary NullPointerException when validating a stack trace.

The problem is in CrashReportCategory.validateStackTrace. The method compares stack trace file names with:

current.getFileName().equals(source.getFileName())

However, StackTraceElement.getFileName() may return null. If current.getFileName() is null, crash report generation itself crashes with:

[11:49:53] [Render thread] [FabricLoader/ERROR]: Uncaught exception in thread "Render thread"
java.lang.NullPointerException: Cannot invoke "String.equals(Object)" because the return value of "java.lang.StackTraceElement.getFileName()" is null
	at knot//net.minecraft.CrashReportCategory.validateStackTrace(CrashReportCategory.java:127)
	at knot//net.minecraft.CrashReport.addCategory(CrashReport.java:201)
	at knot//net.minecraft.CrashReport.addCategory(CrashReport.java:176)
	at java.base/java.lang.Thread.run(Unknown Source)

This can hide the original crash and prevent Minecraft from producing a proper crash report.

Suggested fix:

Use a null-safe comparison for the file name:

Objects.equals(current.getFileName(), source.getFileName())

instead of:

current.getFileName().equals(source.getFileName())

Patch:

-            if (current.isNativeMethod() == source.isNativeMethod() && current.getClassName().equals(source.getClassName()) && current.getFileName().equals(source.getFileName()) && current.getMethodName().equals(source.getMethodName())) {
+            if (current.isNativeMethod() == source.isNativeMethod() && current.getClassName().equals(source.getClassName()) && Objects.equals(current.getFileName(), source.getFileName()) && current.getMethodName().equals(source.getMethodName())) {