omerc inverse: fix division

Test case https://oss-fuzz.com/testcase-detail/5739351578771456 of
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=13894
Credit to OSS Fuzz

Author: rouault

src/projections/omerc.cpp

@@ -97,6 +97,10 @@ static PJ_LP e_inverse (PJ_XY xy, PJ *P) {          /* Ellipsoidal, inverse */
         u = xy.y * Q->cosrot + xy.x * Q->sinrot + Q->u_0;
     }
     Qp = exp(- Q->BrA * v);
+    if( Qp == 0 ) {
+        proj_errno_set(P, PJD_ERR_INVALID_X_OR_Y);
+        return proj_coord_error().lp;
+    }
     Sp = .5 * (Qp - 1. / Qp);
     Tp = .5 * (Qp + 1. / Qp);
     Vp = sin(Q->BrA * u);

test/gie/builtins.gie

@@ -3801,6 +3801,13 @@ expect  0.000898315 -0.001808739
 accept  -200 -100
 expect  -0.000898315 -0.001808739
 
+-------------------------------------------------------------------------------
+operation +proj=omerc   +R=1 +lat_0=1 +lat_1=2 +no_rot
+-------------------------------------------------------------------------------
+direction inverse
+accept  0 1e200
+expect  failure errno invalid_x_or_y
+
 
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 Ortelius Oval