Don't bother checking for NULL functions

This can't happen, and it breaks the thread stuff.

src/syncterm/libjxl.c

@@ -28,16 +28,10 @@ bool load_jxl_funcs(void)
 	Jxl.ResizableParallelRunnerDestroy = JxlResizableParallelRunnerDestroy;
 	Jxl.ResizableParallelRunnerSetThreads = JxlResizableParallelRunnerSetThreads;
 	Jxl.ResizableParallelRunnerSuggestThreads = JxlResizableParallelRunnerSuggestThreads;
+	Jxl.status = JXL_STATUS_NOTHREADS;
+#else
+	Jxl.status = JXL_STATUS_OK;
 #endif
-	if (Jxl.DecoderSetParallelRunner == NULL ||
-	    Jxl.ResizableParallelRunner == NULL ||
-	    Jxl.ResizableParallelRunnerCreate == NULL ||
-	    Jxl.ResizableParallelRunnerDestroy == NULL ||
-	    Jxl.ResizableParallelRunnerSetThreads == NULL ||
-	    Jxl.ResizableParallelRunnerSuggestThreads == NULL)
-		Jxl.status = JXL_STATUS_NOTHREADS;
-	else
-		Jxl.status = JXL_STATUS_OK;
 
 	return true;
 }