avcodec/aacdec_fixed: Fix multiple runtime error: shift exponent 127 is too...

avcodec/aacdec_fixed: Fix multiple runtime error: shift exponent 127 is too large for 32-bit type 'int'

Fixes: 1851/clusterfuzz-testcase-minimized-5692607495667712

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

libavcodec/aacdec_fixed.c

@@ -370,7 +370,9 @@ static void apply_dependent_coupling_fixed(AACContext *ac,
                     shift = (gain-1024) >> 3;
                 }
 
-                if (shift < 0) {
+                if (shift < -31) {
+                    // Nothing to do
+                } else if (shift < 0) {
                     shift = -shift;
                     round = 1 << (shift - 1);