Clear var nullability in loops more accurately #KT-14977 Fixed

compiler/testData/diagnostics/tests/senselessComparison/noExplicitType.kt

@@ -0,0 +1,15 @@
+fun readLine() = "x"
+
+fun foo() {
+    var line = ""
+
+    while (<!SENSELESS_COMPARISON!>line != null<!>) {
+        line = readLine()
+
+        if (<!SENSELESS_COMPARISON!>line != null<!>) {
+            bar()
+        }
+    }
+}
+
+fun bar() {}

compiler/testData/diagnostics/tests/senselessComparison/noExplicitType.txt

@@ -0,0 +1,5 @@
+package
+
+public fun bar(): kotlin.Unit
+public fun foo(): kotlin.Unit
+public fun readLine(): kotlin.String