decompiler: fixed incorrect line numbers in dumped mapping

testData/results/TestClassSimpleBytecodeMapping.dec

@@ -58,12 +58,12 @@ class 'pkg/TestClassSimpleBytecodeMapping' {
 }
 
 Lines mapping:
-12 <-> 2
-14 <-> 3
-17 <-> 5
-21 <-> 8
-22 <-> 9
-23 <-> 10
-25 <-> 12
-26 <-> 13
-31 <-> 18
+12 <-> 5
+14 <-> 6
+17 <-> 8
+21 <-> 11
+22 <-> 12
+23 <-> 13
+25 <-> 15
+26 <-> 16
+31 <-> 21