fix: Fix failing unit tests for row count and single row render condition

Author: NathanZlion

src/table/internal.tsx

@@ -498,7 +498,7 @@ const InternalTable = React.forwardRef(
 
     const colIndexOffset = selectionType ? 1 : 0;
     const totalColumnsCount = visibleColumnDefinitions.length + colIndexOffset;
-    const headerRowCount = hierarchicalStructure?.rows.length ?? 1;
+    const headerRowCount = hierarchicalStructure?.rows.length || 1;
 
     return (
       <LinkDefaultVariantContext.Provider value={{ defaultVariant: 'primary' }}>

src/table/thead.tsx

@@ -142,7 +142,7 @@ const Thead = React.forwardRef(
     };
 
     // No grouping - render single row
-    if (!hierarchicalStructure || hierarchicalStructure.rows.length === 1) {
+    if (!hierarchicalStructure || hierarchicalStructure.rows.length <= 1) {
       return (
         <thead className={clsx(!hidden && styles['thead-active'])}>
           <tr