fix null reference bug and handle escaped escape characters in string tokenization

src/UglyToad.PdfPig.Tests/Parser/PageContentParserTests.cs

@@ -6,6 +6,7 @@
     using PdfPig.Graphics;
     using PdfPig.Graphics.Core;
     using PdfPig.Graphics.Operations.General;
+    using PdfPig.Graphics.Operations.SpecialGraphicsState;
     using PdfPig.Graphics.Operations.TextObjects;
     using PdfPig.Graphics.Operations.TextPositioning;
     using PdfPig.Graphics.Operations.TextShowing;
@@ -153,6 +154,33 @@ ET";
             Assert.Equal(EndText.Value, result[3]);
         }
 
+        [Fact]
+        public void HandlesEscapedLineBreaks()
+        {
+            const string s = @"q 1 0 0 1 48 434
+cm BT 0.0001 Tc 19 0 0 19 0 0 Tm /Tc1 1 Tf (   \(sleep 1; printf ""QUIT\\r\\n""\) | )
+            Tj ET Q";
+
+            var input = StringBytesTestConverter.Convert(s, false);
+
+            var result = parser.Parse(input.Bytes);
+
+            Assert.Equal(9, result.Count);
+
+            Assert.IsType<Push>(result[0]);
+            Assert.IsType<ModifyCurrentTransformationMatrix>(result[1]);
+            Assert.IsType<BeginText>(result[2]);
+            Assert.IsType<SetCharacterSpacing>(result[3]);
+            Assert.IsType<SetTextMatrix>(result[4]);
+
+            Assert.IsType<SetFontAndSize>(result[5]);
+            var text = Assert.IsType<ShowText>(result[6]);
+            Assert.IsType<EndText>(result[7]);
+            Assert.IsType<Pop>(result[8]);
+
+            Assert.Equal(@"   (sleep 1; printf ""QUIT\r\n"") | ", text.Text);
+        }
+
         private static string LineEndingsToWhiteSpace(string str)
         {
             return str.Replace("\r\n", " ").Replace('\n', ' ').Replace('\r', ' ');

src/UglyToad.PdfPig.Tests/Tokenization/StringTokenizerTests.cs

@@ -247,6 +247,20 @@ are the same.)";
             Assert.Equal(@"this does not end with bracket", AssertStringToken(token).Data);
         }
 
+        [Fact]
+        public void HandlesEscapedEscapeCharacters()
+        {
+            const string s = @"(   \(sleep 1; printf ""QUIT\\r\\n""\) | )";
+
+            var input = StringBytesTestConverter.Convert(s);
+
+            var result = tokenizer.TryTokenize(input.First, input.Bytes, out var token);
+
+            Assert.True(result);
+
+            Assert.Equal(@"   (sleep 1; printf ""QUIT\r\n"") | ", AssertStringToken(token).Data);
+        }
+
         private static StringToken AssertStringToken(IToken token)
         {
             Assert.NotNull(token);

src/UglyToad.PdfPig/Fonts/Parser/Handlers/Type1FontHandler.cs

@@ -98,7 +98,7 @@
             }
 
             Encoding fromFont = null;
-            font.Match(x => fromFont = x.Encoding != null ? new BuiltInEncoding(x.Encoding) : default(Encoding), x =>
+            font?.Match(x => fromFont = x.Encoding != null ? new BuiltInEncoding(x.Encoding) : default(Encoding), x =>
             {
                 if (x.Fonts != null && x.Fonts.Count > 0)
                 {

src/UglyToad.PdfPig/Tokenization/StringTokenizer.cs

@@ -109,6 +109,7 @@
                         if (isEscapeActive)
                         {
                             builder.Append(c);
+                            isEscapeActive = false;
                         }
                         else
                         {