LALSimIMRPhenomX.c build error with GCC9

Job #723793 failed for 4af4488d:

 ../../../../lalsimulation/lib/LALSimIMRPhenomX.c: In function 'XLALSimIMRPhenomXPCalculateModelParametersFromSourceFrame':
../../../../lalsimulation/lib/LALSimIMRPhenomX.c:1521:33: error: 'Nz_Jf' may be used uninitialized in this function [-Werror=maybe-uninitialized]
 1521 |      REAL8 XdotQArun     = tmp_x*QArunx_Jf + tmp_y*QAruny_Jf + tmp_z*QArunz_Jf;
      |                            ~~~~~^~~~~~~~~~
../../../../lalsimulation/lib/LALSimIMRPhenomX.c:1495:20: error: 'Nx_Jf' may be used uninitialized in this function [-Werror=maybe-uninitialized]
 1495 |          QArunz_Jf = -Nx_Jf;
      |          ~~~~~~~~~~^~~~~~~~
cc1: all warnings being treated as errors