Allow reusing an ImageProvider and Font on multiple documents

@@ -3,6 +3,7 @@
 ## 3.4.1
 
 - Fix Nunito font parsing
+- Allow reusing an ImageProvider and Font on multiple documents
 
 ## 3.4.0
 
@@ -19,7 +20,7 @@
 
 ## 3.3.0
 
-- Implement To be signed flieds
+- Implement To be signed fields
 - Improve Text rendering
 - Add individual cell decoration
 - Improve Bullet Widget

@@ -128,14 +128,11 @@ class Font {
   PdfFont? _pdfFont;
 
   PdfFont? getFont(Context context) {
-    if (_pdfFont == null) {
+    if (_pdfFont == null || _pdfFont!.pdfDocument != context.document) {
       final pdfDocument = context.document;
       _pdfFont = buildFont(pdfDocument);
     }
 
-    assert(_pdfFont!.pdfDocument == context.document,
-        'Do not reuse a Font object across multiple documents');
-
     return _pdfFont;
   }
 

@@ -57,8 +57,10 @@ abstract class ImageProvider {
     if (effectiveDpi == null || _cache[0] != null) {
       _cache[0] ??= buildImage(context);
 
-      assert(_cache[0]!.pdfDocument == context.document,
-          'Do not reuse an ImageProvider object across multiple documents');
+      if (_cache[0]!.pdfDocument != context.document) {
+        _cache[0] = buildImage(context);
+      }
+
       return _cache[0]!;
     }
 
@@ -69,8 +71,10 @@ abstract class ImageProvider {
       _cache[width] ??= buildImage(context, width: width, height: height);
     }
 
-    assert(_cache[width]!.pdfDocument == context.document,
-        'Do not reuse an ImageProvider object across multiple documents');
+    if (_cache[width]!.pdfDocument != context.document) {
+      _cache[width] = buildImage(context, width: width, height: height);
+    }
+
     return _cache[width]!;
   }
 }