Fix assert and code typo

Author: MihaZupan

src/libraries/System.Private.CoreLib/src/System/SearchValues/Strings/Helpers/RabinKarp.cs

@@ -103,7 +103,6 @@ private readonly int IndexOfAnyCore<TCaseSensitivity>(ReadOnlySpan<char> span)
         {
             Debug.Assert(typeof(TCaseSensitivity) != typeof(CaseInsensitiveUnicode));
             Debug.Assert(span.Length <= MaxInputLength, "Teddy should have handled short inputs.");
-            Debug.Assert(_buckets is not null);
 
             ref char current = ref MemoryMarshal.GetReference(span);
 
@@ -119,6 +118,7 @@ private readonly int IndexOfAnyCore<TCaseSensitivity>(ReadOnlySpan<char> span)
                     hash = (hash << HashShiftPerElement) + TCaseSensitivity.TransformInput(Unsafe.Add(ref current, i));
                 }
 
+                Debug.Assert(_buckets is not null);
                 ref string[]? bucketsRef = ref MemoryMarshal.GetArrayDataReference(_buckets);
 
                 while (true)

src/libraries/System.Private.CoreLib/src/System/SearchValues/Strings/Helpers/StringSearchValuesHelper.cs

@@ -47,7 +47,7 @@ private static bool ScalarEquals<TCaseSensitivity>(ref char matchStart, string c
         {
             for (int i = 0; i < candidate.Length; i++)
             {
-                if (TCaseSensitivity.TransformInput(candidate[i]) != Unsafe.Add(ref matchStart, i))
+                if (TCaseSensitivity.TransformInput(Unsafe.Add(ref matchStart, i)) != candidate[i])
                 {
                     return false;
                 }

src/libraries/System.Private.CoreLib/src/System/SearchValues/Strings/SingleStringSearchValuesThreeChars.cs

@@ -207,8 +207,6 @@ private int IndexOf(ref char searchSpace, int searchSpaceLength)
             }
 
         ShortInput:
-            Debug.Assert(searchSpaceLength < Vector128<ushort>.Count);
-
             string value = _value;
             char valueHead = value.GetRawStringData();