fixes #14444; add genLineDir before assignment (#21201)

* fixes #14444; add `genLineDir` before raises

* add a test case

* fixes differently

compiler/ccgstmts.nim

@@ -1620,6 +1620,7 @@ proc genAsgn(p: BProc, e: PNode, fastAsgn: bool) =
     initLoc(a, locNone, le, OnUnknown)
     a.flags.incl(lfEnforceDeref)
     a.flags.incl(lfPrepareForMutation)
+    genLineDir(p, le) # it can be a nkBracketExpr, which may raise
     expr(p, le, a)
     a.flags.excl(lfPrepareForMutation)
     if fastAsgn: incl(a.flags, lfNoDeepCopy)

tests/errmsgs/t14444.nim

@@ -0,0 +1,14 @@
+discard """
+  matrix: "--hints:off"
+  exitcode: "1"
+  output: '''
+t14444.nim(13)           t14444
+fatal.nim(51)            sysFatal
+Error: unhandled exception: index out of bounds, the container is empty [IndexDefect]
+'''
+"""
+
+when true: # bug #14444
+  var i: string
+  i[10] = 'j'
+  echo i