ltrace: Fix a NULL string use

This case is likely to happen when mod == NULL so print it when
we are computing modname and symname

Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-oe/recipes-devtools/ltrace/ltrace_git.bb

@@ -25,6 +25,7 @@ SRC_URI = "git://github.com/sparkleholic/ltrace.git;branch=master;protocol=http
            file://0001-Add-support-for-mips64-n32-n64.patch \
            file://0001-configure-Recognise-linux-musl-as-a-host-OS.patch \
            file://0001-mips-plt.c-Delete-include-error.h.patch \
+           file://0001-move-fprintf-into-same-block-where-modname-and-symna.patch \
            "
 S = "${WORKDIR}/git"