signature null values fix.

lib/views/widgets/e_signature/e_signature.dart

@@ -19,7 +19,8 @@ class ESignature extends StatefulWidget {
   final bool showShadow;
   final String title;
 
-  const ESignature({Key? key, required this.title, required this.oldSignature, this.backgroundColor, this.onSaved, this.onChange, this.showShadow=true, required this.newSignature}) : super(key: key);
+  const ESignature({Key? key, required this.title, required this.oldSignature, this.backgroundColor, this.onSaved, this.onChange, this.showShadow = true, required this.newSignature})
+      : super(key: key);
 
   @override
   State<ESignature> createState() => _ESignatureState();
@@ -66,7 +67,7 @@ class _ESignatureState extends State<ESignature> {
             decoration: BoxDecoration(
               color: widget.backgroundColor ?? (context.isDark ? AppColor.background(context) : Colors.white),
               borderRadius: _editable ? const BorderRadius.only(topLeft: Radius.circular(10), topRight: Radius.circular(10)) : BorderRadius.circular(10),
-              boxShadow: widget.showShadow? [BoxShadow(color: Colors.black.withOpacity(0.05), blurRadius: 10)]:null,
+              boxShadow: widget.showShadow ? [BoxShadow(color: Colors.black.withOpacity(0.05), blurRadius: 10)] : null,
             ),
             child: Column(
               crossAxisAlignment: CrossAxisAlignment.center,
@@ -89,7 +90,7 @@ class _ESignatureState extends State<ESignature> {
                         .onPress(() async {
                       if (_editable) {
                         signature = await _controller!.toPngBytes();
-                        if (widget.onChange != null) {
+                        if (widget.onChange != null && signature != null) {
                           widget.onChange!(signature!);
                         }
                       }
@@ -103,7 +104,7 @@ class _ESignatureState extends State<ESignature> {
                         height: 135.toScreenHeight,
                         width: MediaQuery.of(context).size.width,
                         padding: const EdgeInsets.only(bottom: 8),
-                        child: signature != null ? Image.memory(signature!) : ImageLoader(showDefaultIcon: true,boxFit: BoxFit.contain, url: URLs.getFileUrl(widget.oldSignature)??''),
+                        child: signature != null ? Image.memory(signature!) : ImageLoader(showDefaultIcon: true, boxFit: BoxFit.contain, url: URLs.getFileUrl(widget.oldSignature) ?? ''),
                       )
                     : AbsorbPointer(
                         absorbing: !_editable,