Clean up numbers reading code in SVGParser

Source/svg/SVGParser.swift

@@ -1516,29 +1516,37 @@ private class PathDataReader {
     private func readData() -> [Double] {
         var data = [Double]()
         while true {
-            while !isNumStart() {
-                if !isAcceptableSeparator(current) {
+            skipSpaces()
+            if let value = readNum() {
+                data.append(value)
+            } else {
                 return data
             }
-                if getPathSegmentType() != nil || readNext() == nil {
-                    return data
-                }
-            }
-            if let double = Double(readNum()) {
-                data.append(double)
-            }
         }
     }
 
-    fileprivate func readNum() -> String {
-        var chars = [current!]
-        var hasDot = current == "."
+    private func skipSpaces() {
+        var ch = current
+        while ch != nil && "\n\r\t ,".contains(String(ch!)) {
+            ch = readNext()
+        }
+    }
+
+    fileprivate func readNum() -> Double? {
+        guard let ch = current else {
+            return nil
+        }
+        if (ch >= "0" && ch <= "9") || ch == "." || ch == "-" {
+            var chars = [ch]
+            var hasDot = ch == "."
             while let ch = readDigit(&hasDot) {
                 chars.append(ch)
             }
             var buf = ""
             buf.unicodeScalars.append(contentsOf: chars)
-        return buf
+            return Double(buf)
+        }
+        return nil
     }
 
     fileprivate func readDigit(_ hasDot: inout Bool) -> UnicodeScalar? {
@@ -1658,13 +1666,6 @@ private class PathDataReader {
         }
     }
 
-    fileprivate func isNumStart() -> Bool {
-        if let ch = current {
-            return (ch >= "0" && ch <= "9") || ch == "." || ch == "-"
-        }
-        return false
-    }
-
 }
 
 fileprivate extension String {