Fix exponent parsing, remove impossible (?) case

(cherry picked from commit 02da42f90b8a912047c00479df789563853cfeee)

worldedit-core/src/main/antlr/com/sk89q/worldedit/antlr/Expression.g4

@@ -60,10 +60,11 @@ DEFAULT : 'default' ;
 fragment DIGIT : [0-9] ;
 fragment SIGN : [+-] ;
 fragment EXP_CHAR : [eE] ;
-fragment DECIMAL : '.' DIGIT+ ( EXP_CHAR SIGN? DIGIT+ )? ;
+fragment EXPONENT : EXP_CHAR SIGN? DIGIT+ ;
+fragment DECIMAL : '.' DIGIT+ ;
 
 // All numbers are treated the same. No int/dec divide.
-NUMBER : ( DIGIT+ DECIMAL? | DECIMAL ) ;
+NUMBER : ( DIGIT+ DECIMAL? | DECIMAL ) EXPONENT? ;
 
 ID : [A-Za-z] [0-9A-Za-z_]* ;
 

worldedit-core/src/main/java/com/sk89q/worldedit/internal/expression/invoke/CompilingVisitor.java

@@ -612,14 +612,9 @@ class CompilingVisitor extends ExpressionBaseVisitor<MethodHandle> {
 
     @Override
     public MethodHandle visitConstantExpression(ExpressionParser.ConstantExpressionContext ctx) {
-        try {
-            return ExpressionHandles.dropData(
-                MethodHandles.constant(Double.class, Double.parseDouble(ctx.getText()))
-            );
-        } catch (NumberFormatException e) {
-            // Rare, but might happen, e.g. if too many digits
-            throw ExpressionHelper.evalException(ctx, "Invalid constant: " + e.getMessage());
-        }
+        return ExpressionHandles.dropData(
+            MethodHandles.constant(Double.class, Double.parseDouble(ctx.getText()))
+        );
     }
 
     @Override