GetStringUTFChars() may fail
GetStringUTFChars() may fail

GetStringUTFChars() can fail, returning NULL. Make sure we do not trip
over it.

Change-Id: I2d6b9c72c353c2423042fd035087f0d57fdc08ca
Signed-off-by: Robert Varga <934bee5bfb2180d3ffa181ef3ed7d341cfd7e2b7@hq.sk>

vpp-dev/vpp,vpp-dev/vpp,chrisy/vpp,muharif/vpp,muharif/vpp,vpp-dev/vpp,FDio/vpp,vpp-dev/vpp,chrisy/vpp,GabrielGanne/vpp-flowtable,GabrielGanne/vpp-flowtable,chrisy/vpp,FDio/vpp,muharif/vpp,milanlenco/vpp,GabrielGanne/vpp-flowtable,GabrielGanne/vpp-flowtable,chrisy/vpp,milanlenco/vpp,GabrielGanne/vpp-flowtable,FDio/vpp,chrisy/vpp,muharif/vpp,FDio/vpp,vpp-dev/vpp,chrisy/vpp,milanlenco/vpp,FDio/vpp,GabrielGanne/vpp-flowtable,chrisy/vpp,milanlenco/vpp,FDio/vpp,vpp-dev/vpp,milanlenco/vpp,vpp-dev/vpp,muharif/vpp,FDio/vpp,milanlenco/vpp,FDio/vpp,muharif/vpp,chrisy/vpp