Fix lineSpecialForm

lineSpecialForm now correctly handles omission of the color argument
as well as line-continuation behaviour.

This fixes part 1 of #4875

Author: Vogel612

Rubberduck.Parsing/Grammar/VBAParser.g4

@@ -571,10 +571,13 @@ withStmt :
 ;
 
 // Special forms with special syntax, only available in VBA reports or VB6 forms and pictureboxes.
-lineSpecialForm : expression whiteSpace ((STEP whiteSpace?)? tuple whiteSpace?)?
-     MINUS (STEP whiteSpace?)? tuple whiteSpace?
-	 (COMMA whiteSpace? expression)? whiteSpace?
-	 (COMMA whiteSpace? lineSpecialFormOption)?;
+// lineSpecialFormOption is required if expression is missing
+lineSpecialForm : expression whiteSpace ((STEP whiteSpace?)? tuple)?
+    whiteSpace? MINUS whiteSpace?
+	(STEP whiteSpace?)? tuple whiteSpace?
+	(COMMA whiteSpace? expression? whiteSpace?)?
+	(COMMA whiteSpace? lineSpecialFormOption)?
+;
 circleSpecialForm : (expression whiteSpace? DOT whiteSpace?)? CIRCLE whiteSpace (STEP whiteSpace?)? tuple (whiteSpace? COMMA whiteSpace? expression)+;
 scaleSpecialForm : (expression whiteSpace? DOT whiteSpace?)? SCALE whiteSpace tuple whiteSpace? MINUS whiteSpace? tuple;
 pSetSpecialForm : (expression whiteSpace? DOT whiteSpace?)? PSET (whiteSpace STEP)? whiteSpace? tuple whiteSpace? (COMMA whiteSpace? expression)?;

RubberduckTests/Inspections/ThunderCode/ThunderCodeInspectionTests.cs

@@ -20,7 +20,7 @@ public class ThunderCodeInspectionTests
         [TestCase(0, @"Public Sub foo()
 End Sub")]
         [TestCase(0, @"Public Sub foo bar()
-End Sub")]
+End Sub")] // Correctly provokes a parser error
         public void NonBreakingSpaceIdentifier_ReturnsResult(int expectedCount, string inputCode)
         {
             var func = new Func<RubberduckParserState, IInspection>(state =>