efi_loader: fix GetNextVariableName

Our current implementation of GetNextVariableName() first collects all EFI
variables. If none is found at all hexport_r() returns a zero length string
terminated by \0 and the value 1 as number of bytes in the returned buffer.

In this case GetNextVariableName() has to return EFI_NOT_FOUND.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Alexander Graf <agraf@suse.de>
diff --git a/lib/efi_loader/efi_variable.c b/lib/efi_loader/efi_variable.c
index d94a5f6..e0d7f57 100644
--- a/lib/efi_loader/efi_variable.c
+++ b/lib/efi_loader/efi_variable.c
@@ -383,7 +383,8 @@
 		list_len = hexport_r(&env_htab, '\n',
 				     H_MATCH_REGEX | H_MATCH_KEY,
 				     &efi_variables_list, 0, 1, regexlist);
-		if (list_len <= 0)
+		/* 1 indicates that no match was found */
+		if (list_len <= 1)
 			return EFI_EXIT(EFI_NOT_FOUND);
 
 		variable = efi_variables_list;