Issue #1348 fix regression: IMDCT_ivas_fx: Assertion observed with LTV test
# Basic info
<!--- Add commit SHA used to reproduce-->
- Float reference:
- Encoder (float):006def7eafc49d3771b6a4d7360af86493b6b5d
- Decoder (float):006def7eafc49d3771b6a4d7360af86493b6b5d
- Fixed point:
- Encoder (fixed): 9d464c09e759faca9675056ef6be07fbcfd3fe50
- Decoder (fixed): 9d464c09e759faca9675056ef6be07fbcfd3fe50
# Bug description
With the changes made as part of MR !1369 (Issue #1348), LTV crashes are observed.
LTV CI pipeline: [Pipeline · SA4 / Audio / IVAS BASOP · GitLab](https://forge.3gpp.org/rep/sa4/audio/ivas-basop/-/pipelines/56498)
Crash is observed in the decoder:
**_IVAS_dec: lib_dec/dec_tcx_fx.c:3475: IMDCT_ivas_fx: Assertion \`extract_h( L_shr( xn_buf_fx_32\[( ind + ( overlap / 2 ) ) + nz\], q_diff ) ) == 0 || extract_h( L_shr( xn_buf_fx_32\[( ind + ( overlap / 2 ) ) + nz\], q_diff ) ) == -1' failed._**
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