avcodec/acelp_pitch_delay: Fix runtime error: value 4.83233e+39 is outside the...

avcodec/acelp_pitch_delay: Fix runtime error: value 4.83233e+39 is outside the range of representable values of type 'float'

Fixes: 1902/clusterfuzz-testcase-minimized-4762451407011840

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpegSigned-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/acelp_pitch_delay.c

@@ -135,7 +135,7 @@ float ff_amr_set_fixed_gain(float fixed_gain_factor, float fixed_mean_energy,
         ff_exp10(0.05 *
               (avpriv_scalarproduct_float_c(pred_table, prediction_error, 4) +
                energy_mean)) /
-        sqrtf(fixed_mean_energy);
+        sqrtf(fixed_mean_energy ? fixed_mean_energy : 1.0);
 
     // update quantified prediction error energy history
     memmove(&prediction_error[0], &prediction_error[1],