Make internal span to nullable type in sequential grid

Author: cheonjaeung

grid/src/commonMain/kotlin/com/cheonjaeung/compose/grid/GridScope.kt

@@ -30,11 +30,7 @@ interface GridScope {
 
 internal object GridScopeInstance : GridScope {
     override fun Modifier.span(span: (GridItemSpanScope.() -> Int)?): Modifier {
-        return this.then(
-            HorizontalVerticalGridSpanElement(
-                span ?: HorizontalVerticalGridParentData.DefaultSpan
-            )
-        )
+        return this.then(HorizontalVerticalGridSpanElement(span = span))
     }
 
     override fun Modifier.align(alignment: Alignment): Modifier {

grid/src/commonMain/kotlin/com/cheonjaeung/compose/grid/HorizontalVerticalGridParentData.kt

@@ -6,11 +6,10 @@ import androidx.compose.ui.Alignment
  * A data class to contain modifier options of item at the specified position.
  */
 internal data class HorizontalVerticalGridParentData(
-    var span: GridItemSpanScope.() -> Int = DefaultSpan,
+    var span: (GridItemSpanScope.() -> Int)? = null,
     var alignment: Alignment = DefaultAlignment
 ) {
     companion object {
-        internal val DefaultSpan: GridItemSpanScope.() -> Int = { 1 }
         internal val DefaultAlignment: Alignment = Alignment.TopStart
     }
 }

grid/src/commonMain/kotlin/com/cheonjaeung/compose/grid/HorizontalVerticalGridSpanModifier.kt

@@ -7,7 +7,7 @@ import androidx.compose.ui.platform.InspectorInfo
 import androidx.compose.ui.unit.Density
 
 internal class HorizontalVerticalGridSpanElement(
-    val span: GridItemSpanScope.() -> Int
+    val span: (GridItemSpanScope.() -> Int)?
 ) : ModifierNodeElement<HorizontalVerticalGridSpanNode>() {
     override fun create(): HorizontalVerticalGridSpanNode {
         return HorizontalVerticalGridSpanNode(span)
@@ -35,11 +35,11 @@ internal class HorizontalVerticalGridSpanElement(
 }
 
 internal class HorizontalVerticalGridSpanNode(
-    var span: GridItemSpanScope.() -> Int
+    var span: (GridItemSpanScope.() -> Int)?
 ) : Modifier.Node(), ParentDataModifierNode {
     override fun Density.modifyParentData(parentData: Any?): Any {
         val p = parentData as? HorizontalVerticalGridParentData ?: HorizontalVerticalGridParentData()
-        if (p.span == HorizontalVerticalGridParentData.DefaultSpan) {
+        if (p.span == null) {
             p.span = span
         }
         return p