Fixed 2 bugs in Join Lines

idea/testData/joinLines/declarationAndAssignment/blankLineBetween.kt

@@ -0,0 +1,5 @@
+fun foo() {
+    <caret>val v: Int
+
+    v = 10
+}

idea/testData/joinLines/declarationAndAssignment/blankLineBetween.kt.after

@@ -0,0 +1,4 @@
+fun foo() {
+    val v: Int<caret> 
+    v = 10
+}

idea/testData/joinLines/declarationAndAssignment/commentBetween.kt

@@ -0,0 +1,5 @@
+fun foo() {
+    <caret>val v: Int
+    // variable v
+    v = 10
+}

idea/testData/joinLines/declarationAndAssignment/commentBetween.kt.after

@@ -0,0 +1,4 @@
+fun foo() {
+    val v: Int<caret> // variable v
+    v = 10
+}