util: check for NULL parameter in virFileWrapperFdCatchError

This reverts 8927c0ea qemu: fix a crash when save file can't be opened
and allows virFileWrapperFdCatchError to be called with NULL instead.

src/qemu/qemu_driver.c

@@ -2908,8 +2908,7 @@ qemuDomainSaveMemory(struct qemud_driver *driver,
 
 cleanup:
     VIR_FORCE_CLOSE(fd);
-    if (wrapperFd)
-        virFileWrapperFdCatchError(wrapperFd);
+    virFileWrapperFdCatchError(wrapperFd);
     virFileWrapperFdFree(wrapperFd);
     VIR_FREE(xml);
 
@@ -3365,8 +3364,7 @@ doCoreDump(struct qemud_driver *driver,
 cleanup:
     VIR_FORCE_CLOSE(fd);
     if (ret != 0) {
-        if (wrapperFd)
-            virFileWrapperFdCatchError(wrapperFd);
+        virFileWrapperFdCatchError(wrapperFd);
         unlink(path);
     }
     virFileWrapperFdFree(wrapperFd);

src/util/virfile.c

@@ -369,7 +369,7 @@ virFileWrapperFdClose(virFileWrapperFdPtr wfd)
 void
 virFileWrapperFdCatchError(virFileWrapperFdPtr wfd)
 {
-    if (wfd->err_msg)
+    if (wfd && wfd->err_msg)
         VIR_WARN("iohelper reports: %s", wfd->err_msg);
 }