interfering talker flag not triggered on short test vector
# Basic info
<!--- Add commit SHA used to reproduce -->
* Encoder (float): 311956f3
* Encoder (fix) : e1432023
* Decoder: 311956f3
# Bug description
The interfering talker flag is not triggered on stvST48c.wav, leading to a lower quality for stereo content during interfering content.
in the figure below, from top to bottom :
- synthesis (stvST48c.wav)
- floating point element mode
- fixed point element mode

# Ways to reproduce
IVAS_cod -STEREO 24400 48 .\ivas-codec\scripts\testv\stvST48c.wav bit24400
(Clear steps or refer to a failing automated test, e.g. with a pipeline link)
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tagging @malenovsky, @multrus for awareness
issue