swresample/resample: replace assert by av_assert

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libswresample/resample.c

@@ -447,7 +447,7 @@ static int invert_initial_buffer(ResampleContext *c, AudioData *dst, const Audio
     *out_idx = c->filter_length + (c->index >> c->phase_shift);
     *out_sz = 1 + c->filter_length * 2 - *out_idx;
     c->index &= c->phase_mask;
-    assert(res > 0);
+    av_assert1(res > 0);
 
     return res;
 }