imc: use correct position for flcoeffs2 calculation

flcoeffs2[pos] should be the log2 of flcoeffs1[pos].
flcoeffs1[0] can be 0 here, thus flcoeffs2[pos] gets set to -inf,
causing problems further down.

This seems to have been copied from imc_decode_level_coefficients in
commit 4eb4bb3 without updating the position.

Reviewed-by: Michael Niedermayer <michaelni@gmx.at>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>

libavcodec/imc.c

@@ -426,7 +426,7 @@ static void imc_decode_level_coefficients_raw(IMCContext *q, int *levlCoeffBuf,
 
     pos = q->coef0_pos;
     flcoeffs1[pos] = 20000.0 / pow (2, levlCoeffBuf[0] * 0.18945); // 0.18945 = log2(10) * 0.05703125
-    flcoeffs2[pos] = log2f(flcoeffs1[0]);
+    flcoeffs2[pos] = log2f(flcoeffs1[pos]);
     tmp  = flcoeffs1[pos];
     tmp2 = flcoeffs2[pos];