Fix SIGFPE crash - Initialize mRawAudioSampleRate and validate sample…

[damiangr]

Problem

The ImpulseResponse class can trigger SIGFPE (floating point exception) crashes due to division by zero when mRawAudioSampleRate is uninitialized or zero.

Solution

• Initialize mRawAudioSampleRate to 0.0 in both constructors
• Add validation in constructor to check if input sampleRate <= 0.0
• Add validation in _SetWeights() to check if mSampleRate <= 0.0
• Return early with ERROR_OTHER state when invalid sample rates detected

Impact

• Prevents crashes in downstream applications (e.g., NeuralAmpModelerPlugin)
• Maintains existing API and behavior for valid inputs
• Minimal code changes focused on safety

Testing

• ✅ Tested on Windows (Visual Studio 2022, x64 Release build)
• ⚠️ Limited macOS testing due to environmental constraints (VMware Sonoma 14.7.2 + Xcode 16.2)
• 📝 Recommend CI testing for comprehensive macOS validation

Files Changed

• dsp/ImpulseResponse.cpp: Added initialization and validation checksessions or IR files with invalid sample rates.