Move filter assertion closer to where it's used

The only unsafe part of filter_signal_in_place_fixed_size_simdx4 now
should be making sure the CPU supports it at runtime.

crates/ntscrs/src/filter.rs

@@ -267,6 +267,12 @@ impl TransferFunction {
         scale: f32,
         delay: usize,
     ) {
+        // Ensure the chunks are actually of equal length
+        let width = signal[0].len();
+        for i in 1..ROWS {
+            assert_eq!(signal[i].len(), width);
+        }
+
         let mut z = initial.map(|initial| S::load(&self.initial_condition(initial)));
 
         let mut num: [f32; 4] = [0f32; 4];
@@ -407,12 +413,6 @@ impl TransferFunction {
     ) {
         let filter_len = usize::max(self.num.len(), self.den.len());
 
-        // Ensure the chunks are actually of equal length
-        let width = signal[0].len();
-        for i in 1..ROWS {
-            assert_eq!(signal[i].len(), width);
-        }
-
         match filter_len {
             // Specialize fixed-size implementations for filter sizes 1-8
             1 => self.filter_signal_in_place_fixed_size::<1, ROWS>(signal, initial, scale, delay),